I think you just need to be a named pilot on his insurance policy that way if something happens they cannot come after you. Should be a simple process for the owner to do this. The ins company will probably require an experience form from you which will break down your time in types. I think am acceptable rate for instruction would be $30-40 an hour. I guess it would depend on how often he wants to fly. Fly more often = lower hourly rate. My two cents.