Relevant thread.
But here's a brief checklist of what to look for in a consumer set:
- At least one each of all the relevant inputs, depending on where you live: composite, s-video, component (if US), SCART (if Europe)
- Standard definition (480i/576i). 480p sets are somewhat desirable if PS2 is a major concern of yours (PS2 probably has the most even split of 480i and 480p games of any mainstream console). I'd avoid HD CRTs.
- Good working condition. Test out any set before you buy. Look for bad geometry (wavy or distorted image when it should be straight), bad colors, bad overscan, etc. See if you can correct any potential issues by messing around with the service menu, which you'd have to Google to learn how to access for each specific model. If you want some examples of problems to look for and an easy way to test for them, look up the info on the "240p Test Suite" posted in the thread linked above.
If you really want to go all out, you can seek out professional studio monitors as suggested above.