I'd agree with Louie that the pawn shops can be a good place to find decent instruments, but would advise one caution.
Take a tuner with you!
The shops around my area have "learned" that it's a good idea to have their instruments close to being tuned; but also that stringed instruments "feel" like they have a good action if they're about a half step (or more) flat. What feels really nice in the shop may be a "bone eater" when you bring it up to pitch.
Best thing is to take a decent player and a tuner.