Sometimes asking around at the club will get you a lead on good used stuff. Trainers usually get beat up though, so you'll come closer finding good second planes that way. What I find is more common is the trainer for sale on craigslist that has 10 years of garage dust on it from a guy who started learning and quit. You can figure on replacing the batteries and often the radio isn't worth anything, but engines and airframes and most flightline accessories survive storage quite well.