Heed TG's advice. There are a lot of old Santanas around-and for a good reason. They are good bikes made with good steel and they last. Like any other bike, make sure the frame isn't bent or cracked, the fork is in good shape, headset smooth, etc. The unique things on Santanas aren't to be worried about. Most good tandem shops carry the stuff you'll need and if not, you can call Santana directly.