One of my guys when I owned a body shop did side work for cash doing roofing for a friend of his. I get a call on a Saturday from him in the hospital, he fell off the roof. Wanted to have me tell the workmans comp and insurance that he was working for me in the shop and tripped and fell. He broke bones in his neck, and was going to be out of work for a while. Are you kidding? No way, working for cash has drawbacks and this is just one of them. Some folks can get away with under the table, but when it crashes, it can hurt in more ways than one.