I had problems with a contractor once, but he learned a few important lessons. I insisted when we signed the contract that it have penalty clauses, otherwise I would not do business with him. For each day past a set date he had to pay me $100 a day until the job was completed. Further, when he got slow I insisted that I pay his subs directly and deduct that amount from anything I owed him. Finally, in our town it is illegal (yes illegal) for a homeowner to make a final payment to a contractor until the town approves the job. This gives you added protection.