It's a crap shoot, and if you approach it like that, it's fine. I recently bought a used motorcycle from a Craigslist seller. Before finding the one I bought, I looked at several that should have been better bikes, but had issues. One looked like it had been rewired by an untrained monkey. It ran fine, but I really wouldn't want to be around the first time it got caught in the rain. I could rewire it without too much problem, but it would take the better part of twelve hours and probably a couple hundred dollars of parts to do it right. The next one was OK, but the seller discovered that he couldn't find the title and, oh by the way, the title was in the name of some guy from Alaska who sold it to him and... Oh, well. The one I bought had issues, too, but not as bad as the wiring, so it was the one I bought. Time consuming? Yeah. PITA? Yeah, but not really any different from the routine back when things got bought and sold by classified ads in the newspaper.
Those aren't musical instruments, but it's the same thing across the board. Some people, like the guy I finally bought from, will tell you pretty much everything right and wrong as far as he knows. He isn't you and won't necessarily care about what you care about, but he will be honest. Other people, like the guy with the wiring problem or especially the guy with the "lost" title are not going to be as honest. That's just the nature and range of people who exist.
