For what it's worth: I've bought two old trainers w/engines off Ebay, both local pickup, both from experienced flyers who were just trying to pare down their hangars. Both of them purr and are well-broke in. It was nice I was able to meet them face-to-face because it gave me confidence in who and what they were all about.

So heed RC Ken's advice, but if you're lucky enough to live in a metro area where you can meet the seller (search Ebay by zipcode, ask to pick up to save shipping) you'll probably get a good deal. They'll have to face you at the field if it's no good! Otherwise, assume you're buying "as-is" and take your chances. My experience is only about buying trainers with tainer engines, not high-priced Saitos etc.