You will have to call your local Porsche dealer and inquire about that since rates vary. At the same time you can have them remove the engine cover and inspect for leaks, check that any updates have been done and give you an estimate on remaining rotor, brake and tire life. Be sure and get everything in writing to help with the negotiations and to understand your future expenses. The seller might be willing to deduct the cost from the price if you do purchase the car. I remember a thread that discussed the various rev limiter read outs and if someone doesn't add that here I'll try to find it later.

Edit: Here is one I remember. PIWIS Analysis Log

And see if you can talk to the former owner. Sometimes that can be very useful.