Heres an idea. Do it for that 30 a square. Make sure he knows that there is no liability insurance or anything. Then fall of the roof of the lower part. Then call a laywer!
Whenever I do jobs on the side, I always write in the contract that the homeowner understands this is a cash only job and no insurance is to be used. If any damage occurs to the house or any injuries to anyone working on the roof, homeowner accepts full responsiblity.
Anyways, I wouldnt do it for less than 2 grand and thats if I were by myself and it was a side job.