If you are on a tight budget, go with a 924 or early 944. These cars generally have cheaper parts and less gizmos to replace when they go bad.
I'd say the 83 944 is the most economical. Problems with power steering tends to be common and expensive. Since the 83 model does not have p/s, that's one less thing to go wrong. No power tilt roof (another common problem), no cruise control, no pwr seats and no pwr locks. The 83 is the most simple and basic of the 944 series. Many parts for early 944s (83-85/1) are cheaper than later 944s.
Later 944s (85.5+) have aluminum suspension components and an updated interior w/ better a/c. There are many other little improvements on later 944s. All 944s (84+) have power steering, which many people (but not me
) value.
944 Turbos are fast. A lot of bang for the buck.
All 944s are galvanived, so rust shouldn't be much of a problem, if there is rust, don't buy it. There are many rust-free cars out there.
Checklist time:
-Buy a car with maintainance records.
-A recent clutch replacement is a plus
-recent t-belt/water replacement is good
-have a Porsche shop look over the car before purchase
Pay a little more for a good car, project cars get expensive, really fast
BTW, I really like early RX-7s.