Don't be afraid to ask questions. Take a flashlight and get on the ground. Check under carpet for rust, door posts, inner fenders and tailgate area. Check fluid levels. Look for leaks. Don't make your final decision on a leak though. That's what these things do when they sit for any time.
Look for signs of body work. Take it for a spin. If you decide to buy it ask if he has any parts that go with it (just in case, might be able to get a few parts you can sell off to offset the price).
If it runs good and looks as good as it does in the pics then I would say this is easily a $4500-5000 Bronco. Take your time and look for additions that bring it up another 1000 or so.
-bn