The usual inspection would be cracks on the frame especially the BB area. Wear on the rims can give you an idea as to how truthful the owner is on the mileage of the bike. Any creaking noise from the crank, headset and seat post as these are tensioned areas. It wouldn't hurt to test ride it. As for the price, try this: How It Works - Used Bikes - BicycleBlueBook.com
"The will to win means nothing without the will to prepare." - Juma Ikangaa, 1989 NYC Marathon winner
"Common sense is not too common these days."
"Cheap things have no value, valuable things are not cheap." - Fortune Cookie