Wow...140K isn't affordable in your area? That's what they're getting for 3-4K sq/ft homes? Thanks for the perspective.
As for developing:
1) Make sure your money is solid (you don't want to run out midstream or if a delay occurs...and something always delays you)
2) Get to know your local governing body (County Commissioners, Building Dept., etc)
3) Don't overpay for the land. Figure your development costs and then figure your per-lot development costs. You'd like your lot cost to be less than or equal to 20-25% of your total sales price (home & lot).
4) Interview a few, and find a good, engineer. This guy can make life easier for you...or a living hell.
5) Do not assume that you will sell all your houses in the first month!!! If you finance the project, you likely won't get your money until the final few houses sell...this can take a long time.
That's a brief "top of my head" sketch. I'll try to come up with some more for you.