Charles... another approach is for you to buy the home, do the rehab,etc. Make sure that market value includes your acquisition cost, plus holding cost (taxes, insurance, etc), plus your rehab cost, and then about a 25% to 35% profit margin on your total investment. This is about what you would (or should) expect to make on your own flip.
You can structure the deal as an option to buy the house upon completion for a certain amount as calculated above. The cost of the option would be an amount to cover you if they back down (example: $10,000 or 10% of the expected final price). This way, if they back down for any reason, they loose the "option" amount, which will the allow you to sell their "custom" home to someone else and have less risk.
I am not an attorney, so make sure you get an attorney if you decide to go this route. I am sure one or more will comment on this idea for you.
If the numbers work, I would do this deal myself!
Good luck.