Although the villagers begin gathering stone for construction as soon as an agreement is struck between the village and the "scholars", the process may seem slow to the magi. Not all of the villagers will participate in this, and even those who do will not devote all of their time to it, since they have to take care of their livelihood as well.
A few things become clearer as work begins.
First, there is the matter of time. It quickly becomes obvious that work will proceed slowly if using only villagers. When asked, those involved think they can complete the two small houses by the end of summer, or perhaps mid-fall at the worst. This will obviously not be fast enough for the magi, as they will probably want to have at least one (if not both) of the large houses up and habitable by that time. But the villagers do not have the tools nor the skill to dig up cellars in the stone of the plateau. The villagers also seem a bit uncertain about building two-story houses. So it seems that outside help will need to be hired.
A second thing that needs to be decided is the layout of the buildings. Take a look at the sketch of the area around the oak and let me know where you'd like to put the houses and garden. Remember that the elders need to agree to the location, but this does not seem like something that will cause problem. Once the location has been agreed to, I will add the houses to the sketch.
A third problem may quickly crop up, that of money. From what I can see in the Pooled Resources thread, the magi have about 36 pounds of silver. Of that, a bit over 1 pound has already been spent in temporary accomodations and food since arriving on the island (there are 4 magi and 12 mundanes to feed). If the accomodations remain the same, 5 more pounds will have been spent by the end of summer for that, leaving 30 pounds.
As building materials are purchased and workers hired (including villagers), it looks like the cost of construction will look like this. Each of the small house will cost about 4 pounds to build. The villagers don't need much outside assistance for these, so most of the expense is from wood brought from outside of the plateau (or even the island).
The large house may prove much more expensive, for the structure cannot be that of the simple village houses, which does not work well for a second floor. So more outside workers are needed, much more lumber as well, and specialized workers/tools to dig up the cellars (it is preferable to do this before putting up the structure of the house). So each large house may end up costing 20 pounds or more.
Compounding the money problem in the short term, Trond and his crew needed some the magi's silver to purchase their first cargo. This immobilized about 15 pounds, leaving only 15 pounds for the construction itself. Of course, the merchanting business will bring back money over the course of the summer, in the order of about 5 pounds per month of profits. But that still leaves only 30 pounds available, by the end of summer, for the construction. Money will keep flowing in over time, but there is initially not enough to construct and outfit all of the buildings.
In short, the magi must make some decisions about what to prioritize, or how to make work less expensive, or how to raise more money. Note that Bernhard will stop by a few times over the summer, so he may be consulted about this if needed (e.g. if you decide sell raw vis for silver).
The goal here is not to get bogged in details. I gave you some numbers to work with just so that you would get a sense of scale regarding the construction and living costs at this time.