The other day, my young neighbor, who had just moved into the neighborhood and liked to throw loud parties, asked me for a favor. She had hosted another one of her wild parties, but then got called out of town for work. She asked if I could clean up the mess at her place and said she would pay me. I agreed, since some extra cash is always helpful.

Cleaning up the disaster in her house took me two full days. When she returned, I went over to get paid, but she suddenly claimed that we had never made any agreement. We argued for about half an hour, but she kept denying it.

Fine. If she wanted to be difficult, I could be firm. I left, but I came back twenty minutes later with something prepared. I knocked on her door again and handed her a written invoice for $250, along with printed copies of the messages where she had clearly asked me to clean her house.

I also showed her a small-claims court filing form that I had filled out, explaining that if she didn’t pay by the next day at noon, I would submit it.

She got flustered and tried to claim it was all a misunderstanding, but I simply wished her a good evening and went home. About ten minutes later, she came to my door with the full $250 plus an extra $20 for the trouble.