While it's true that any old CRT will work, you'll probably want to be a bit more choosy with your TV. You'll want to make sure that it has at least RCA hookups and if it supports component, even better. S-Video hookups are good too. Some TVs only have the stupid RF hookup and those are pretty universally bad choices.
There are also TVs that won't allow you to use the menu without a remote, these are also generally bad choices. Pay attention to the buttons on the TV's interface and if it's unclear whether you can use the menu or not, see if you can demo it in store.
Depending on how lanky your arms are and what your ability to carry weight is, you can get a pretty big and good TV. I'm about 6 feet tall and I can carry a 27" TV as long as the mold is designed correctly and it isn't too heavy for me, like more than 80-85 pounds. Ideally you should get a TV that's basically as large as you can carry comfortably. If you're taking it to venues, you might have to travel over significant distances with that TV, so you'll be earning that venue fee. Keep that in mind when choosing.