First time I heard someone actually "want" to drive a heavy clutch under that advice. Anyways, welcome to the Board! #1 is do you want a Project to learn on? Or do you want a turn key? Most of us here bought cheap (under 1K) and learned on them. It's an expensive process but the knowledge and experience is priceless. Put your location in your Profile so we know what part of the world your in, and maybe you'll have one of us nearby you can test drive.
It's a V8, so don't expect to compare it to a Prius. I believe some are getting between 15-18mpg. I don't monitor because I just accept it's a V8 and sucks on gas.
FYI, you "could" spend up to $60,000 on a Concourse low mileage GTS. Also, as an another FYI, I got my 1983 928S for $900. Here's the thread:
http://forums.pelicanparts.com/porsche-928-technical-forum/583848-900-1983-us-928s-latest-leo928s.html
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1981 Porsche 928 "Euro" Auto Gunsmoke Metallic Flat - Black Interior
1983 Porsche 928S "US" Auto Light Bronze (Copper) Metallic - Brown Interior **SOLD**