Welcome to BHQ!
IMO I would look for the newest banshee you can afford. If your not wanting a bone stock bike, I would find one that already has pipes, cool head, filters, welded crank, paddles etc.... Look for normal wear and tear, cracks or bends in the frame, unusual oil leaking or motor covered in oil.
Any good banshee owner will be able to tell you everything about there bike they are selling...
If your looking at some online post your links on here.