In my previous home, I put up a spy camera in my window and hit record each morning, after a few unpleasant encounters with my white trash neighbor.
I didn't want him to know about it, but of course my kids found it and announced it to the whole world. It worked out anyway, because he knew my house was under surveillance (and that I was armed) so he and his scumbag friends decided to pick easier targets.
You should be able to rig something up for under $100.