For a "PPI" you find a mechanic who knows the partiocular car. You discuss with them that you want a car inspection to make a decision about buying the car. I typically recommend a body/paint inspection, a complete CPO inspection and a dump of the DME for error codes and over-revs/abuse.

You need to usually drive the car to the mechanic.

Cost is $150 -350, or more- depending. (Off topic, but on point: Recently I am seeing more people doing compression and leak down on the 996TTs as it is getting 'longer in the tooth', and trying to understand over-revs leads to more complete inspections.500-600 just for this part, but they replace plugs while in there.)

The evap code you are concerned with: what was done to fix this? Could just be a gas cap issue... if it is still under warranty, I'd not be concerned with this....