If you're on a tight budget, a mennonite house makes sense. They are fine and the mennonites are, as far as I know skilled, honest and quick builders, but you will not get a very nice house without adding a bit to the basics they provide.
If I were to buy a basic mennonite house, I would do the following relatively cheap improvements:
1. a layer of tar paper.
2. a layer of R-11 insulation.
3. 3/4" drywalls.
4. consider "real" windows, at least in bedroom or other rooms where a/c might be installed in the future.
Alternatively, talk to local builder Jim Hanna, who has built many very nice and reasonably priced wooden houses on the island.