Do try e-Bay, search for "vintage or antique banjo" and see what comes up. I've seen some awfully nice banjos go for less than $500, some of which would have taken more money to properly set up. Buying on e-Bay has the disadvantage of not being able to play the instrument first, to hear how well it sounds. And I suppose there a lot of judgment and experience that goes into risking a bid. But if you don't live nearly a fine old-time music store, such as Elderly in Michigan, e-Bay may be your best bet. You can always check "completed items" to see what "antique banjos" have gone for recently.

Otherwise, I'd probably also recommend the Saga-10 as a reasonably priced beginner's instrument for old-time playing.

Cheerily,
Charley Noble, who plays an S.S. Stewart Orchestra Model banjo