Hello welcome to the forum, and hopefully the world of air cooled Porsche's
the 964 is a great car and good ones are appreciating fast , so find a good one and buy it ! it was a great step forward in development from all that went before, much more power , better corrosion resistance better handling and creature comforts, all that stuff unfortunately means extra weight though. They were known as a bit leaky in the oil dept, so have a good look on the inside of the under tray and if dry, so far so good. The dual mass flywheel has also been known as a weakness,and are expensive to change, I would think most 964's with a dodgy flywheel have had them changed by now though, so you are probably ok.Make sure all the electrics work on the car, including seats ! Have a good look round and under the car and drive it. If all seems ok get an independent specialist to give a report on the car, not cheap but could save you thousands. Good luck PS I am not a 964 expert/owner, I have a 993, but the '64 was the next best thing