And where do you want to live?
I had initially proposed doing a poll for the tribunal, however the Tribunal is just one aspect of the question. In or near a city? On the coast? What do we want around us? What size aura? What magnitude of aura? What is our mundane wealth source?
Those are a few questions I can think of off the top of my head, I'm sure more will come up during discussion.
As I mentioned in my introduction of Petronius, using the Rhine tribunal would be good for me, but specific tribunal is not a big issue for me.
The character would be more interested in a secure and stable home as a first criteria. Good access to research material (such as a Mercurian site or something similar) would be a bonus and serve as an initial incentive to setp up there. Otherwise, he can be there due to the political machinations of his pater.
City could work for him, although not ideal since he's got a normal Gift with its attendant social consequences. A source of Terram vis would be great, and I'm somewhat partial to cliffs of other rocky areas (that does not preclude a coastal area).
Not looking for a huge aura -- anything positive will do for him.
For mundane wealth, since he's good with Terram he could easily learn Touch of Midas to supply the covenant with mundane wealth, provided we have a reasonable explanation for the income. The would be only 2 pawns of vis for a big chunk of gold. Maybe combined with a skilled goldsmith that create jewelry? That would obscure the source of the gold somewhat.
I'm not terribly dependent on location - infact a weak-ish aura is perhaps a good thing, as I am planning to work actively towards strengthening it.
Perhaps a central location with one aura and some minor spots in the vicinity with seperate auras, for my research?
Mountains are always nice, especally with a Terram magus in the covenant.
Itinerants minor hook could be good one as it allows many stories to be told and started easily. Secondary income is a nice as it allows flexibility and safety - and if you start to make savings or improvements with magic there are more options. Trade and fishing would be natural combination with Kale clan stopping by every year at our friendly covenant.
Magical aura is nice to have, but it doesn't need to be very high - aura of 3 is pretty nice. Relatively peaceful and small community out of the way with only minor problems would be rather nice. Perhaps a village on border of Rhine and Novgorod tribunals?
Contentious and highly political places are not ones where my character would be likely to go - unless he just did not realise how full of strife that place could be.
If we go with a Rhine covenant, a potential site is Lake Constance, a very large lake (39 miles long) at the border of Germany, Switzerland and Lichtenstein. The lake is the the foot of the Alps, so lots of mountains around (meaning caves, valleys, cliffs, etc.)
The city of Konstanz has the only bridge across the Rhine in the region, so there is a lot of trade going through. The city of Bregenz is at the other end of the lake. Both cities have good roman history.
From an Hermetic perspective, a covenant located there could be either in the Rhine of the Greater Alps tribunals, and possibly a trade point between the two tribunals.
Might not fit whan Jonathan has in mind, but I'm just throwing it out as a possibility.
BTW, what year are we using? Since we'll probably be moving fairly rapidly, I would suggest that starting a few decades before ArM5 "official" year may not be a bad idea. Makes it easier to use published materials if we want to evolve the magi without too much research.
Not that it really matters, but canonically there are two magical Mercere in a chapterhouse on Lake Constance, it's a chapter of the Covenant of the Icy North, in the Tribunal of the Greater Alps.
The primary challenge of placing a covenant in the Greater Alps is meeting the wealth requirement, which really isn't all that much of a problem from a game mechanics perspective. The wealth requirement is 10 pawns of vis per magus, which "buys a chair" at the Tribunal, although no vis is exchanged or given. The vis source is vetted by Quaesitores. The idea is that this proves you're rich enough to stay here without upsetting the status quo. In practice no new covenants are formed, but as I see it, the primary impediment is having the vis source to do it. Every covenant is 'taxed' 2 pawns per year for the senior members of House Guernicus and House Mercere. These two pawns need to be factored in as part of the vis source as well, per the insert on page 10 of Sanctuary of Ice. So the vis necessary is Magi x 10 +2
The political or Hermetic culture stories I can envision us creating in this environment, given the canonical setting, would be that we are nouveau riche. We would be extremely young, and we would be extremely unfamiliar with the culture of the Greater Alps when we enter 'play'. We would be allowed in because we meet the legal requirements to do so, having bought a chair for all the starting magi. We were enterprising, we discovered vis sources in your post gauntlet years, exploited them and then capitalized to combine our resources into a covenant. Those kinds of stories could be fun. The Tribunal also has a custom called ostracism, which kicks someone out of the Tribunal based on votes. If you're tiring of your character, you could effectively write them out at the next Tribunal and they have to go make their way elsewhere in the world, and work up a different character. For example, if we have no mundane source and rely on magic, converting vis to mundane wealth, I can see how we would be considered gauche and unsophisticated.
I don't have any strong opinions on the year. The location is also not something that is super important to me. I will tend to be the agent provocateur in this setup process putting everyone's ideas through the crucible and trying to come to a common ground on what we see the environment looks like, hence my discussion above about Lake Constance and The Tribunal of the Greater Alps.
I don't have Sanctuary of Ice, but from what I see in Guardians of the Forests the lake is right at the border between the tribunals. Do you have an exact location for the chapterhouse? It might be at the southern edge of the lake, so if we were to set up at the northern end we might still claim to be part of the Rhine tribunal. Would fit the political machinations of Petronius' pater, as a way to claim sources of vis and block incursions from the Alps. (Octavius' argument: It's "just" a chapterhouse, and chapterhouses are not real covenants. Furthermore, the northern side of Lake Constance is clearly in our Tribunal, so the Alps have no business claiming vis sources there.)
Makes for a interesting Hermetic political playground, if one of the characters is interested in that angle.
Rorschach is about 10 km from modern-day Lustenau, on the southern side of the lake.
My preference is that no individual participant have that much political power, if you're wanting your character to avoid politics it seems to be counter-intuitive to have him, through his parens, heavily involved in the placement and selection of the covenant site and using as a pawn to interfere in another Tribunal. That's kind of what I'm getting from this suggestion. If everyone else doesn't mind that, I don't have a problem with it. I think, though, this could impact all the players and generally speaking I'd hoped to avoid political entanglements of one participant affecting all the participants.
As I mentioned, I don't have SoI, so I didn't know there were any other covenants so close. The character is not looking for political entanglements, far to the contrary. However, the way I've written his pater is as a political beast who is using Petronius as a pawn to advance his goals. Petronius doesn't realize this, he is too driven-minded by his research to realize how much politics affect who he is asked to help or not.
Like I wrote before, I don't have a specific site in mind, I was just throwing out a possibility without knowing the interaction with the Greater Alps tribunal.
Want me to search for another potential site? Did you (or anyone else for that matter) have someplace in mind that I could do some investigating on? 
What is at the site is probably more important to me than the actual location of the site.
I'm currently writing a version of my character that uses Guild Trained (ie, comes from the Rhine Tribunal) only because this has been suggested, not because it is central or important to the character.
You mentioned an aura, preferably low so you could scale up your experiments, if I'm remembering correctly (I have a lot of stuff going on in my head right now). Maybe pockets of other auras nearby...?
Exactly.
Also, what sort of library do we plan on starting out with?
I'm ok with anything from nothing (we have to start from scratch and write/trade for anything we want) to fairly large-ish.
Also, it looks like we'll have a bunch of Bonisagi, so we'll probably have ties with Durenmar 
As any greedy scientist I want a +5 aura, remote, central, out of the way and accessible (at the same time 
) lots of vis, unlimited money and a huge library 
More seriously. I think wealth and good (hermetic) trade connections is more important than aura for me. A specialist would need a market to work in to earn his living, and good trade relations to trade the books he needs/wants.
Since he wants to live forever any location with negative modifiers to health is completely unacceptable to him. Mountains (with fresh air and a view) is very good. Somewhere in the southern outskirts of the Rhine sounds nice. Rhine is rather full, so in the forests North of Transylvania and like a "Border Post" supported by (and politically in) Novgorod might be nice?
The setting on the Rhine/Greater Alp border was a deja vu, since that is exactly what we played the last time I tried out the concept, so I'd like to avoid that. (It resulted in two tractati on The Code of Hermes. One from the Rhine ("Why mountains are the Natural Borders") and one from the Greater Alps ("On the Superiority of Rivers as Borders") Much fun was had.
Depends on what power level we start on. Is this high power, low or medium? Does that make a difference?
Do we have certain very low quality books for free? I'm thinking he Q5L5 Arts text we might give to an apprentice. No one wants to spend build points on those typically, they only want the best possible texts. I find that is reasonable from a player perspective but makes little sense from a game perspective of why all these extremely well developed books exist. The Q15L15 Summa on an Art being the kind of classic. It's only 30 build points. By comparison that only gets a 6 pawn per year vis source.... Or in stocks that will be 150 pawns of vis, which is why I suggested we not buy vis stocks with build points. How much would a Q15L15 summa cost? Has anyone figured that out?
I would go for low-medium, but I don't really feel it makes that much difference for a new covenant. We're going for a new covenant, so it should probably be Spring?
The rules make it easy to write high-quality, low-level summae. That said, I don't have a problem with a library with primer-level books with low qualities (Q4 to Q6). Their probably throw-away books for most established covenants, so I agree that we should have them for essentially free. (Or maybe a token 1 build point for each? Except, are we even going to be counting the build points?)
A bunch of tractatus (which are more useful than summae) as well and some mid-level summae (L10-12). It's probably easier to get hold of mundane Abilities books, as these can easily be copied by mundane scribes. Lab texts are usually quite usuful, for spells mostly but some items are also nice.
How many players/magi do we expect for the covenant? We could have each one prepare part of the library, based on each magus' interests.
Ok, I'm going to suggest some stats for the covenant, quick an dirty. That's just a basis for discussion, not anything I want.
If we go for low-medium level (let's say 300-400 build points), we could divide it between:
Possible boons and hooks (minor boons/hooks are not identified, major and free ones are identified in parantheses):
Let me stress again that those are just a list of the boons/hooks that seemed possible for the covenant while quickly going through the list.
The value proposition for summae really change depending on whether you know the Art or not. If you take someone with an Art score of 12, with 78 XP, the value of the L15Q15 summa is greater than an equivalent bp expenditure in tractatus: to reach 15th level requires 120 xp, so one can add 30 xp or 42 xp for the same bp cost. If the Art is 0, that value proposition is huge, 30 build points gets you 30 xp or 120 xp.
It's looking like 4 or 5 magi, maybe 6? 300-400 bp is pretty low. While we are starting a spring covenant, I'm thinking that our back story period of 5 to 10 years post gauntlet could have been spent acquiring some of these resources to bring into the covenant, including identifying vis sources nearby our covenant site. We can of course be a poor spring covenant that grows into a powerful summer/autumn covenant over the life, but having only 300 bps means we hussle more soon after covenant founding to fill in the gaps in the covenant than study. That has an impact to the growth, if our characters are scrimping for scarce resources.
Sure, we can start with more resources, I certainly have nothing against that! We can easily double or even triple the numbers, but I think the proportions for library/vis/other remain pretty much valid.
This would give something like:
Any ideas regarding the boons and hooks?
My comment was more along the lines of saying the choices we make as far as selecting and allocating a build point amount will set the stage for some of the things we do starting off. Do we do more stories up front about scrounging for resources to fill in gaps because of low build points, or do we presume it was done in our back story and increase the amount? See how the covenant is already shaping the stories? 
Understood. Some stories about resources make for good sidetracks, particularly if all the magi of the covenant are very focused on their own research. If nothing comes up to disturb them once in a while, then most of what they'll do will be spend time in the lab experimenting. Having your elbow jostled once in a while by an unwanted and unrelated story makes for a more realistic advancement of the magi.
Random idea: Considering the nature of the saga, maybe having a "fragmented" aura might fit well. Small, relatively weak pocket auras scattered around a somewhat wider area. Could be related to different Roman ruins in an area. Good candidates for something this would be the areas around Trier (described in GotF), Mainz, Koln (Cologne). Having each magus' sanctum some distance from each other has some advantages from an in-character perspective, but also saga-wise, since each of the magi will essentially have a thread on their own. Then the magi meet each other once a season or so, to discuss things related to the covenant's resources (harvesting and splitting off the vis, trading books from each individual libraries, etc.)
Having separated and fragmented auras where each magus occupies a spot difficult to protect with an Aegis. I like it.
So, I've been thinking about my character in the context of a Rhine saga; and it looks like it's Rhine, because you've been the most vocal and no one has naysayed you, so I'll take that as consensus (if anyone else has strong opinions now's the time to voice them). How fragmented and how wide an area are you thinking? I'm kind of thinking about the trader archetype and being around the Deutches Eck which is smack dab in the middle of Mainz and Köln, in Koblenz. He would likely be Gently Gifted, and I could see him trying to setup in Koblenz and be in the bustle of trading activity at the confluence of the Rhine and Mosel.
Speaking to the fragmented aura, perhaps we have a stronger aura in a small location where the ostensible council hall is and it's large enough to house a common lab that is better than what the magi individually can produce? I'm playing in Peregrine_Bjornaer's Canaries are Dying saga, and he made a common lab, by accident, that has too many specializations and is setup for transient use so the intelligence of the user doesn't interfere with the refinement score. We decided to leave it as is, despite the rules limiting the number of specializations from Covenants. I really like it, it has character and it looks like 5 people designed it for their particular needs, it's a hot mess. It breaks Hermetic limits and no one either stops to thinking about it or they don't care. I can see something like that developing over time, and indeed the story of making something like that is an area where we can collaborate without getting in the way of each other and slowing down pacing, as long as we reserve the lab before we start writing stories.