I don't think you can look to the D&D rules for help in simulating anything outside of dungeon-crawling. The trick is to avoid shattering everyone's suspension of disbelief when they see the logical consequences of their magical spells being put to use for straightforward economic gain.
If this is a new community, it's presumably not integrated into a larger society, which implies that the cost of transporting goods to and from it should be immense. (If it's easy to get to, why wasn't it already part of the larger society?)
So, the cost of importing goods should be high, as should the cost of exporting goods. So the community has little going for it except whatever fertile land it rests on. Of course, in a feudal world, few communities do have much more going for them than the land, but definitely think of the community as a Dark Age village, not a Renaissance city-state.
