Well, you have 3 generic choices for used ships:
Civilian - this runs from your generic Star RV and Yachts, to colonization ships
Commercial - couriers, barges, prospectors, and freighters, etc...
Para-Military - may be decommisioned military or scout, most likely without weapons but military sensors could be intact
Your best bet is to make a few tables for each type. Throw some lemons on the list and a few 'jewels in the rough'. The tables don't have to be any bigger than 6 ships per table, but be prepared for the group to want to look through each or to give one a 'test drive'.
Unless you want to get into black market starships...
d20 Star Wars had a nice used ship quirks table I wish I could reprint here for you, but it's copyrighted.
Hope that helped a bit,
Dameon