Not knowing anything about building contracts, I can't give good advice. Sure raises lots of questions. Is "cost" defined in your contract? Materials and sources spelled out? In most states (and with IRS), there is a difference between an employee and a contractor. If he is charging a weekly wage, it seems possible that he is no longer a contractor, but an employee. Is there a time frame and max. cost in the contract? If he cuts back to 30 hours a week, does he still get $800? Whew!