$123 to buy an old safe that might have been empty, and needed to be cut open, is a big risk of money.
Maybe the buyer felt he could crack the safe and had money to play with?
Be that as it may, would you keep all the money?
Probably not, but I'd definitely keep some. I'd be pretty annoyed if the guy wanted to thank me, give me a 50 buck reward, and get all the money back. I don't think I'd go along with that, but I might go along with 50/50, or even just keeping 25%.