Depends which model Porsche you decide on...
The 911 models with the air cooled opposed 6's are the most desired and expensive models...but they hold their value over time so it would be a good investment.
The 944 line (944,951...etc) are great vehicles! Parts can be gotten anywhere (NAPA stores) on the most part and maintance is easy. The watercooled 4-cyl is by no means a slow engine. The turbo'd version is hot and will make the car move.
I would test drive a couple of different models before buying. The price tag is everything so watch out! By the way, Porsche started putting computers in their cars in 1985.5 and after. Fuel injection was standard around 1974 or so.