I think it would largely depend on the type and amount of use the sander has seen. There is one thing to look for, the oldest RO125 models don't have the edge guard. I happen to think the edge guard is worth having. As for wear items, look at the sanding brake and sanding pad(s). These items are fairly inexpensive to replace.
I'd only go for this sander if you're getting a good price and it's in good to fair condition.