If I didn't know much about cars and I wasn't able to buy a new one from a dealer I might get a friend who does know something about bikes to look over my purchase. I've had pretty good luck with Craigslist and if the guy says $20 will do it I don't have enough paranoia at the moment (it's not my money) to say it wouldn't. It's a bicycle. Unless something is bent, broken or missing... ... I could get even more emphatic, use bold type even if you had mentioned make and model (and year) of bike and the asking price.

H