The #1 question is how much to you trust the sellers diagnostics when it comes to your money?
If it becomes too much to handle, then you'll be lucky t get scrap value from a member here. Right now you are buying the "unknown", which is why I said $2k. It's a gamble. You could replace the in tank pump, bleed the brakes, fire her up and she's a strong runner. If you get it home and find major problems, then the condition is "known" and if it's "too much to handle", then it's worth scrap to me.
I personally would only buy a questionable deuce knowing that it could wind up as just a parts truck. Too many things could go wrong and it might just not be worth the cost of getting it running. However, as a parts truck, $1,500 would not be unreasonable. I bought my last parts truck w/w for $2k and I pick from it all the time.
So, if you're willing to take the chance that it could be a strong runner with little investment, that's your call and $1800 is fair. If you think it might be a lawn ornament that you pick from over the next 5 years, then offer him scrap.
Mikey