Builder has agreed to buy my house at the end of construction in eight months if it does not sell.
Problem is he will only buy on land contract. I'm worried about the due on sale clause
As you should be. You must get approval to sell on land contract from your mortgage holders. Kliszlaw.com. Tim Klisz
You need to have a real estate attorney review all of your documents before you give the builder any more money or sign any other documents. It sounds like you already may be in hot water.