You want to look it over before you buy. Does it have all the parts? How about the bobbin case - is it there? Does it work? How's the stitch? Check inside for rust and gunk. Does it have any accessories? Is there a case? Manual? How's the finish on it? Dull, flaky, chipped or shiny and new? How does the motor sound? Run the foot control enough to know if it works for more than a couple minutes. How much are you willing to do to it? Are you willing to pay for servicing the machine?