Mike's comment about state inspection is a good point. Not an issue where I'm at, so I often forget what some people go through.
If you do look at the car... Do check the fault codes AFTER driving it. Do pull the oil filter off to look at the oil for any debris. -You can pull the filter cup off the bottom of the engine and hardly any extra oil will drain out. The car will have to be jacked up or on ramps and you will need an appropriate filter wrench.
Push all the buttons, grab the tires at 6 and 12 and 3 and 9 and check for suspension play. Figure out how to remove the engine cover: Find out that the power steering fluid is below the dipstick, the engine is filthy, leaking oil, and the vacuum hoses are all broken. Along with everything else, it should probably have the water pump replaced, front bumper removed and radiators cleaned, a new engine mount, idler pulleys, DIY starter rebuild (cleaning), transmission oil change, brake flush, window regulators, and new struts.
I think its not worth paying to have a professional PPI done on a $4,500 car, but you could learn a lot if you do it.
Mike has a some good info about buying here:
https://sites.google.com/site/mikefocke2/mikesporscheboxsterwebpages
...but you could probably buy it for $4,500 and drive the poop out of it for the rest of the year without spending more than a few hundred (plus the cost of some awesome tires ...tires matter).