Since the current owner is an indepedent, INSIST that you have access to all the books, esp box office reports.
The first theatre that I looked at buying turned out to have a rep as not necessarily reporting all the admissions.
If you are serious about owning a theatre (sounds like you are), you should hook up with a booker BEFORE you buy.
A booker familiar with the territory will be able to verify what the owner is telling you as far as how feasible the theatre's business drawing area is, competition, etc.
Plus a booker has access to Rentrak and EDI box office info for the theatre (assuming they are currently reporting to one or both).
The booker may also be able to find out what reputation the theatre has with the distributors. A bad theatre rep could possibly make things for difficult to get off the ground, since you are new to the business.
I guess generally I am saying don't always believe everything at face value and/or what the owner says. Do your own homework to verify what he says.
Now that I've said all this negative stuff, here's a positive note wishing you the best and hoping that it turns out to be a good deal for you!!