I'd be a little worried about the fact that the guy seem iffy on if a lot of it even works. Sure, most, if not all, of it probably does, but that's a large wad of cash to drop if the stuff you want the most ends up being broken. Virtual Boys in particular are really prone to having difficult to fix problems when they haven't been taken care of well.

But, yeah, definitely scope things out first. See if the systems and games look really gnarly and beat up, and see if you can spot some valuable games. Regardless, I would try to talk the guy down to at least $300.