Thanks Holly!
Ironically, that's how I found my current tank! It was on Craigs list. My only rule is that it has to have been dry for less than a couple of months. I've heard some real horror stories about glass plates falling away from fully-stocked tanks in to middle of the night because of rotted seals.
I plan to test and possible re-seal if I go the used route. I also think that I am going to be picky about getting an Oceanic tank this time.