I have been looking at an 84 GTC recently. The guy that owns it told me to make him an offer. The car has a 95 inspection sticker on the windshield that has to be replaced, no battery, and a complete interior that needs to be taken care of. How much should I offer him?

A car that hasn't been on the road since the mid 90s has probably got a bunch of problems. Rubber in the tires, bushings and hoses tends to rot and go bad in that kind of time. Was the gas drained or stabilized? How has it been stored? Sounds kind of like its a parts car since an interior redo can cost some serious $$$. Lots of questions to answer your question. Sorry it's not that simple.
I wish you luck with it!

fiddy..
final offer.

I've seen Audi I-5s sit improperly stored for 10+ years and start up on the first try with NO work done to them...