Thanks Terrapin.
I get the impression this guy knows little to nothing about comic books and wouldn't be interested in giving me a list or anything like that. He said he had to dig them out of storage so I'm guessing they are his dads or something. I'm going to see the comics in person before making an offer, and I bet it will be a "here's the bin, I don't know anything about them, make me an offer" sort of situation. If I bring an overstreet price guide with me he will likely start asking me what the guide says they are worth, so that seems like a bad idea (overstreet prices seem inflated compared to ebay).
He wants to sell them all together so I would likely be making a offer price like "a buck a comic". I'm hoping I can get a list of the more valuable comics from that time period, so if we get in a debate about price, I would know "okay I can go a bit higher, there's a Hulk 181 (or whatever) in there" or "Nah I better not go higher, I don't see any valuable comics jumping out at me".
p.s. condition is totally key, you are right. But I'm not sure what to expect on that front just yet. At least with condition it will be evident as soon as I look at them. I'm just worried about not realizing there's an expensive comic in the mix that I've missed.