Looking at buying a VN SS

So an atlas grey VN SS has come up at a decent price that needs some mechanical attention. The seller says that it has only a couple of rust bubbles below the rear window but other than that the body is clean.

Trying to organise to check it out tomorrow night. Is there anything in particular that I should be looking for in this model that tends to go wrong (areas of rust, expensive/hard to get parts etc.)? I'm not too clued up on these things since I've only ever seen one of them up close.

Also, what do you think one would be worth in non-running condition? And how can I tell if it's a genuine SS and not a mockup?

Cheers