I've had several of these beasts pass through my hands including a 1991 Porsche 911 Carrera 2, 1987 Porsche 944 turbo, 1996 Porsche 911 twin turbo, 1988 Porsche 928 S4 as well as numerous others I've been lucky enough to experience.
Can they serve as reliable daily drivers? You bet. Are they more demanding than a Toyota Camry to maintain? You bet.
If I were looking for a daily driver I think the 944 series or 1987-1989 911 Carrera series would be my picks. The 944 is more comfortable than the 911 assuming you like the "sit on the floor" type seating position. The 944 is also quite economical in terms of fuel economy (even the 944 turbo isn't bad in that regard as long as you aren't into the boost all the time... which, I'll admit is difficult.)
The engine in the 944 is a 2.5 liter 4 cyl unit which was NOT built by Audi. The old 2.0 liter 4 cyl engine found in the 924 was an Audi unit and it was not exactly a crowning achievement for either company. The 944 engine was derived from the early 928 V8... half of it at least. ;-) The basic 2.5 engine in the 944 is very reliable and I know of several with more than 300k miles on them. The 944 turbo adds a bit to maintenance levels but I found that it wasn't bad and parts were easy to find and didn't cost an arm and a leg. On the 944 just make sure the timing belt service has been done fairly recently, check the body for prior accident damage as many of these cars have been whacked and in many cases repaired by the blind (or so it seems?!), also check the clutch and gearbox function (I don't like the automatics), suspension, etc. Try to buy an enthusiast's car if you can find one near you. Chances are that you will pay more but it will likely have been maintained far better than one that Joe Schmoe has for sale in his yard.
The 911 is also a great car. The 80's cars were generally well built and reliable. After all, that had many years of development by then. A 911 will easily cost you double or triple the cost of the 944 but it is an iconic sports car so you'll have to pay up a bit. Check for body work, engine/oil leaks, suspension, clutch (post 87 models were hydraulic assist) exhaust and heater boxes etc. The 911 also will require periodic valve adjustments which isn't the end of the world but it will add to your maintenance costs.
The 928... der Land Shark. Fantastic grand touring cars... not really a sports car per se. These cars often get a bad wrap for being unreliable and horrendously expensive to maintain. A well sorted 928 is quite reliable and can be used as a daily driver as long as you are OK with the fuel economy. ;-) Again, I've seen more than a few with 200k-300k miles and still going strong. They are well built although the interiors often tend to show their age with dash/pod cracks, warping panels etc. The body is mostly aluminum (roof and rear quarters are steel) so corrosion isn't usually a problem except around the rear window bases. Again, the newer the better.
Get out and drive them and see what you like the best. Then when you get serious have a well versed Porsche mechanic inspect the car prior to purchase. Good luck!