One immediate thought is that there are many unfinished subdivisions left over from the housing problem where the first few houses were all that were built, creating a big drop in value, cause nobody wants to live in a 2-house subdivision.

Have a real estate or construction attorney review the proposed contract. You could also check public records to see if he really owns the subdivision outright.

There is not really a lot that can be done.

Builders create shell companies all the time for large projects.
This provides a legal buffer between the company and the builder and any assets he may have.

You can sue the shell company, try to take money from it under contract till the cows come home and all you will get are attorney's bills.

The shell company has NO assets, and may not actually own the land.
It contracts with the builder for EVERYTHING.

If one project falls apart, the company is dissolved and the builder starts another one for the next large project.