i agree with what ethan says. being as though we work in a bicycle shop, we find things more often, but there are still things out there. we've had customers come away from yard sales and goodwills with nice cheap bikes. of course, there is more trash than treasure there, so be choosy. always make sure when looking at used (and new bikes from wal-mart, target, etc.) that you make sure that the frame is square. stand behind and in front of the bike and make sure that it's straight, front to back. on used bikes also, look behind the front fork where it meets the actual bike frame. if you see wrinkles in the downtube, don't buy it! i've seen a LOT of older bikes come through the shop with bent frames. another tell tale sign of a bend in that spot, is cracks in the paint on the top tube behind the stem (goose neck for you old timers). it might kind of look like stretch marks in the paint. use your common sense and better judgement and you'll most likely be okay.