I have bought and sold a few ss's that have come up for sale locally. The one thing I would recommend you do is inspect the boards closely before you buy. There will be back-up batteries residing on the mpu or cpu from the factory. If they have never been changed you may have leakage in that board and boards below it/next to it. Also, look closely for burn marks on any boards and any hacks in the area of the boards while you're in there. A visual inspection could save you some grief. If you have an experienced tech. to work with over the phone concerning boards, he can guide you through a test procedure to help identify a bad board. You can either send it in for repair, buy a replacement board if available, or convert to a new board set depending on era. That's just a matter of swapping a board(s) out which is easy - just make sure you ground yourself and use anti-static (esd) bags/box to ship.

Great analogy........