If you paid $740, you got your money's worth. A proper sand/prep/paint job would have costed at least double what you paid. If you can't resolve it between you two, I would just move on and find a better place. If you don't have a written contract on what he was going to do, then you would likely be out of luck, legally. And even if you did take it to court and did win, if he don't have the money, you still won't be paid. My opinion.