We are hiring a DJ through a friend. His services is at a really great price and has asked for cash up front because of the huge discount. Should I be prepared with some kind of agreement for him/us to sign stating that if for some reason he cancels, we get a full refund? Especially since I'm paying him $400 in cash. (He might have his own agreement when we meet with him, but I wanted to be prepared with something in case he doesn't have any paperwork.)