I had a friend who has passed away, that would like a gun I had and he would offer more that it was worth so of course I sold it to him. He would keep it a while and want to trade back for another of my guns, of course they were worth about the same and he would give me $100 boot so I traded him.
After he had it a while he wanted the first gun back, so I traded him and he gave me another $100 boot. He did that several times with other guns, one I got to own 3 times.
George was his name and he once asked me how hot can you load a 9mm Luger round for me. I told him I could load it hot enough to blow up your gun. He said well only make one of them then. I really miss him, I didn't feel guilty about his constant trading, because I restored several for him and didn't charge anything.