Actually, if you're doing this, you have five spices, not four, because you are creating nutmegs.
Nutmeg is a seed, from within a fruit (the flesh of which can be used for various useful purposes, like flavouring candy).
The aril (membrane) around the nutmeg (seed), when dried and separated is traded as a different spice, called mace.
Even if the wiggle room does not exist in your campaign, creating nutmeg fruits naturally creates both spices, because mace and nutmeg are natural components of the fruit, like the pips and skin of an apple.
I agree with your main point, which is that you need to sell in places where the spice is common. I would however suggest that Mythic True Cinnamon is possibly a bad choice, because in Mythic Europe is arguably harvested by Arabs who scare winged serpents out of cinnamon trees using burned borax. There is, therefore, not a lot of it about.
Actually, even now. That stuff you buy in stores and think is cinnamon? It's not "true cinnamon": it's cassia, which is what the Arabs were harvesting in the real world and claiming it was so expensive because they needed to buy borax and risk their lives on it. Mythic Europeans with high theology scores do know the difference, because Moses is commanded to use both types when making anointing oil (assuming that "sweet cinnamon" is true cinnamon).
My big point, really, is that cinnamon's a bad choice, because it's basically treasure seized by force from monsters, unless you can convince people you, for example, are getting serichatum (Serican cinnamon) somehow, because no-one knows where it comes from. Although, people will then wwant to hborn in on your success.
I think it's interesting we never go with local spices. If you were in Hungary, for example, and you made a ton of mustard, you could sell that at a tidy profit an no-one would blink an eye, because mustard takes Richard's example to the other extreme: people expect to be able to get it everywhere. Almonds, too, would work, I think.
Wheat. Just make wheat - now that is something everyone expects to have, in large quantities, everywhere, yet there is always demand for more - especially at times of famine. With just one village, using the "Grow Your Crops In A Day" you can get, what, the worth of 300 villages ? 150 villages ? Now consider that a Typical source of agricultural income for a Covenant is 6 villages; so multiply this by 6... Granted, this isn't as much wealth as a ton of saffron, but how much do you actually need ? If that's not enough to support your covenant, you have one strange covenant....
The whole issue of Hermetic power level becomes relevant here in two ways. First - it's not too hard to create wealth by magical means. So you need to decide whether you really want to try to limit that (soil requires resting, etc). Secondly - it's not too hard to deal with any mundane threat. So you need to decide if you really want to make mundane threats, like pissing off Venice, important things to worry about. I personally think limiting the ability to create wealth is bound to feel artificial and the players are likely to find loopholes, and that mundane threats aren't interesting. I prefer to just let magi create wealth magically however they like, and focus stories on more Mythic stuff. But to each his own.
Thank you - I could have sworn it was "a penny a day for a peasant's wage, which, adjusting for Sundays and holidays, was one mythic pound a year" - but I couldn't find that.
Maybe it's just my regular paranoia kicking in... I would never go with something exotic not made in abundance locally or transited through the Covenant's area in great volume.
Saffron, mustard, pepper, sugar... all extremely expensive and the luxury items in the ArM5's time. I would assume if a new supplier suddenly would appear, attention would follow.
Dark-alley-backstabbing theme with greedy merchants, nobles over a small chest of peppers is a great story to play with companions.
I better fancy a steady income producing solution, where you do not have to
Add Vis to gain silver (e.g.: all creation rituals)
Confront wealthy people with political / military / holy power (e.g.: saffron, false relics)
Invest time after the start (e.g.: cast the bloody spell every day)
Based on Art I tried to collect my ideas.
Animal
Bringing an animal to full maturity is a good start to work with, if your troupe agrees it's not a ritual spell as it is already used with the CrHe 30 Fast Grow spell (MoH pg 39).
-- horses are expensive, although you have to tame and train a good grog can make wonders with the right set of Virtues and Abilities.
-- cattle or oxen, a simple enchanted item can be used to bring a calf to full mature, suddenly you can get meat, bones and skin. Skin is what you will need to make your own books.
Creating an Animal corpse for meat (month) is a bit shady way to earn money. A magical hook where a full-grown dead pig appears ready to be put into a meat pie. (Sausage is a bad idea... due to it will only be there for a month, but a good juicy meat pie... nobody's gonna hold unto that for month.
Wool... I remember a spell or a spell guideline for CrHe, where a non-ritual spell makes a tree grow a new fruit, which is still nourishing... and I cannot find it now. With the same kind of an approach (and Circle, Room spell) overnight all your sheep will be ready for shearing, again and again.
Candles from pig-fat or whale fat. Is there a better whale hunter than the mage (or the magical harpoon) who can drive the whale directly to the shore?
Aquam
In Vino Veritas - a small pond worth of beer or wine for month is MuAq 10 (Base 2 +1 Touch +3 Month). You supply the local taverns and they supply you with silver... although you can easily get into troubles.
Beer, in general, isn't a great idea as in 1215 only a couple of friars are using hops and drinking lager. Everyone else drinks something really horrible. Wine in the other hand is good stuff... it's even produced in England at this time.
Herbam
Any crops grown with Circle of Iðunn will have warping point, but no warping score. You can easily stockpile huge amount of food and supply your Covenant, but when you start to produce huge amounts for the market it will bring attention from the local lord (land being the base for all tax, not to forget things like the Domesday book in England). In less centralized territories it is a great income source, or you find a way not to sell in local markets.
Fruit or Olive orchards would need a minor enchanted item for the Base15 CrHe, but it is a perfect long term income source. Although it might bring attention from local authorities, when suddenly the whole hill is ripe with grapes, olives or walnut.
Dyes go well with your wool investment and again easy to create or help your specialized grogs.
Direct magical linen based manufacturing requires too high finesse rolls, so going with the small magical help route can make your manufactures quite productive... especially if you combine it with the cheap labour (option bellow) for the monotone and work intensive steps.
Corpus
The local hospital ain't the best solution, to put it mildly. I would expect quite heavy church related games to come, when the miraculous recoveries are going to spread like wildfire... and these games to finish with the Quesitor's arrival and with the Tribunal's verdict.
Cheap labour in a dangerous or hidden places: miners in a mine filled with toxic gas, rowers, pearl hunters at the bottom of the sea, woodcutters. Simple investment, but definitely full with risks and good games.
Mentem
The old, 'you have haven't paid the toll' trick built into the gate under which all merchants have the pass. Dirty trick with easy money.
Terram
The 'salt' is one of the best idea I have seen in this forum. Easy to set up, maintain and the grogs can do the manual labour... and it was the first I have told my troupe, as it is used by another Covenant, which is wealthy & powerful already.
Mining non-precious metals is also good income source, especially if you include the smelter and smiting/ manufacturing part.
Making arms and expensive armours is a bloody easy way to get your silver and to sweeten the relationship with the local lord. With couple of Ignem magic circles you can make your smith a really happy man. Adding a specialized room with MuTe25 (Base 3, +1 Touch, +2 Ring, +2 Room) and all metal can be shaped as clay in your secret chain mail mass-producing room.
Sooner or later your Covenant will need specialized glass-workers. Why not include glassware (with some Terram magic help) in your Covenant's income structure? Making a beautiful glass mosaic and gifting it to the Lord, later placed in his inner sanctum, opens up opportunities for nice long-range spying.
On the subject of covenant finances, has anyone noticed that by default cost-savings specialists actually cost more than they save? Unless you take extreme measures, like only hiring rare craftsmen with very high ability scores, then paying them nothing. It gets better with Spring/Winter covenants than with Summer/Autumn covenants, due to lower living costs. This seems rather odd to me - what's the point of cost-savings then?
Let's see, a specialist costs... 2 or 3 pounds a year, by my calculations, depending on whether you are Winter/Spring or Summer Autumn. He saves 1+Craft/2 or Craft (depending on the craft) pounds a year...
Given that elsewhere (Covenants p.88) it says that a Craftsman is considered skilled if he has a Profession score of 6 or more, the specialist does save money. Maybe not a lot, but he does save some...
It's important to understand that a competent craftsman har a score of 6+ in his craft (per C&G, and also mentioned in Covenants IIRC).
That's when you start seeing a bit of a saving
One of the perks to having craftsmen and specialists is that you are producing more in-house and are a bit more protected against, say, the local merchants deciding "those odd folks on the hill really need to pay through the nose if they want our goods cuz, man, they're odd." Prejudice, war, disease, and so forth can really alter the market so bringing it under your roof isn't a bad plan for some security.
I also imagine that a lot of the stuff a covenant might want isn't necessarily off-the-shelf merchandise. Consider all the glassware for a lab; no matter how much you save or don't save in terms of money, it is certainly a lot easier to just have your guy do the special order instead of having to go explain it to the local glassblower, if there actually is one.
A common craftsman with a score of 6 has a net worth of {6/2 - 2.64 = .36£}. Easy enough.
A rare craftsman with a score of 3 has a net worth of {3 - 2.64 = .36£}. Easy enough.
A common craftsman with a score of 10 has a net worth of {10/2 - 5.04 = -.04£}. Hard to get.
A rare craftsman with a score of 5 has a net worth of {5 - 5.04 = -.04£}. Still easy to get
Rare craftsmen can also reduce the Laboratory Upkeep of some free Outfittings Virtues on p116. Superior Equipment and Superior Tools can cost 6-12£ per year together.
With the same kind of an approach (and Circle, Room spell) overnight all your sheep will be ready for shearing, again and again.
Dirty trick with easy money.