Ron,
I'm sorry that Erick had some bad luck with the 'S' that he owned. If you do a little research on this board, you'll find that every time one of these cars comes up, he will discourage the potential buyer. I really believe that he just doesn't care for them, kind of a personal preference thing.
I'm fortunate enough to currently own a 1987 S and absolutely love the car. This is my second Porsche. My first one was a 1986 N/A with 90K miles and my current 944 S has 71K miles. I'm a fanatic about maintenance so I'd like to think I can speak from at least some experience.
Parts for the 'S' in my experience haven't been any harder to find...yet. I live in Dallas and I'm about 20 minutes away from Zims and have been lucky enough to become pretty good buddies with some of the guys over there and they take good care of me.
In terms of the car you're currently looking at: if there are no records and you don't have anywhere to take the car for a good PPI, then keep looking, but then again you'd want records and a PPI on any 14 year old Porsche, wouldn't you?
If you can get someone who's knowledgeable to help you with a PPI and you're satisfied, then you should factor in some inherent costs. Things like the tensioner, belts, tune-up, etc. If you fairly competent with a wrench, you'll be able to do most of your own work, which is the real key to owning these cars and keeping them on the road.
In terms of just owning one? It's a great car and I get compliments all the time. People, even knowledgeable Porsche people seem to appreciate that the 'S' is relatively rare. I went into owning this car with my eyes open and knew that to get it to where I thought it should be would take some time and money. Also, you should know that like golf, perfection is pretty much unattainable unless you have an unlimited budget. There's always some little thing that needs to be fixed or fiddled with or tightened or replaced.
It's not a very 'quick' car but it wasn't designed to be. It was designed as an Autobahn cruiser. It doesn't wake up until about 4500 rpm, then you'll understand why Porsche designed a 16 valve engine for these cars. If you need any more detail on day to day ownership or what I think of the 'S' and the N/A, feel free to email me.
Hope this helps,
Dustin
ballgofar@verizonmail.com