A lot of car of that era rust around the lip that holds the rear window in. I don't think it's a deal breaker, but it might be a way to negotiate the price down a bit.
Go to Collector Car Market Review Pricing
and check out the suggested value. Value is really what you can get it for and how bad you want it, collector car values aren't like newer car blue book pricing. Pricing in guides is partially based on auction and other reportable sales results, but there is some estimating as well.
From what I can see and the description that is somewhere between a #2 and #3 car (IMHO). It's also a Tempest -- there were no LeMans four doors, at least not in 65. That would put it in the $4000-$5000 range, not $6000. Top value for a #2 (remember, most show cars you see are #2 -- a #1 car is a top pro resto trailered to shows, or a museum quality resto) is $5500-$5600.
Would $6K be too much to pay for it? Not if you really like/want it. Print the value and condition guide pages out and take them with you when you look at it though. $5K would be a more fair price, but it really depends on how much you like it and what your other options are. On the plus side it looks ready to roll. If you plan on using it as a daily driver that 326 is going to get old fast, but it will put a smile on your face -- until you hit the gas pumps. You're probably looking at 18 mpg on a good day of interstate travel, keeping it no more than 65 mph (MAYBE 70... but no more!), an average of 15-16 mpg. If more fun is better than more mileage that won't matter...
I'd pay $6K for that one before I'd go for a cheap car that needs a lot of work.