Ok, I believe in your case that the best way to handle this is to contact the builder immediately if you are uncomfortable with this agreement. Notify him that you wish to him to cease finishing the basement as you have had second thoughts and no longer wish to purchase the home. This is a "good faith" move on your part to stop him from wasting anymore time and money on the home. You could offer to allow him to keep a said portion of the payment already made in exchange for disregarding the previous agreement and not going to closing on the home. Since you have not signed the closing papers nor taken possession of the home you will not be in breach of contract on the sale of the home itself but may have a possible breach of this agreement which would only be good up to the amount you paid or the amount he has spent on labor & materials to finish the basement (or the portion of work he has completed thus far). Should he decide to take legal action he would only be able to collect for the work that was done from the time the agreement was signed until the date you requested that he cease all work. This is a very big decision and one that should not be entered into if you have ANY hesitation about. Contact the builder immediately and discuss your options with him of what he would settle for to allow you out of the agreement. Good luck!