I also have a Porsche ( 1987 928 S4) that is the stablemate to my 72 Z. The 928 is my trip/touring car while the Z fulfills my "down and dirty" desire to feel every physical force that accompanies the no frills driving aspects of pure sports cars. No computer assist, no automatic leveling, traction control or completely quiet cockpit...just you, the Z, the sounds and the next demanding road.
In it's day, the 70-72 Z ate the basic 911's lunch. Fiat, MG, Triumph, Lancia all played catch up after it's introduction. 150 hp, great design, superb handling and a great cockpit led to their being forced to the back of the bus. The 996 is a great deal for a cheap "initial" buy in to the Porsche fraternity. Like any German engineered car, they need constant inspection and strict maintenance followup. They will cost more to own, you will not recoup your investment, but like the Z they are made to drive, the harder the better.
For my money, if you are patient, you can find a solid, well taken care of 1st generation Z but you must look everywhere. Get up an hour early, go through craiglist in other cities and states, set up a automatic search engine, go to other unknown listing sites and you will find your car.
I am currently finishing up an 8 month engine refurbish upgrade to my Z. My goal was keeping the stock appearance and just concentrating on engine, trans and suspension enhancements. Rolly the "Zombie" Alberto is masterminding the engine and he is a savant when it comes to squeezing max hp from 4-6 cylinder engines. Rolly is from the Philippines and has two speed shops there that build drift cars for the Asian market.
I will post everything here once we are finished in about 3 weeks. The early Z's are so simple to work on, so simple to up grade that its makes much better sense to buy one if you can't afford both.
Good luck keep us posted.