The first step is to hire him. Being around him could reveal the answers to your questions without coming right out and asking. Then again, a roofing job doesn't take all that long to do. This is a tuff one.
If you have some mutual friends I suppose you could ask them some general questions, but then you run the risk of them figuring out that you're interested before you even know that yourself. Personally I wouldn't do this but I know people that would and would say they were just looking for character refernces before they hire him. That could work.
