What to look for when buying a modern water cooled Porsche 911

1. Have the mechanic do a compression check and a leakdown test. 

2. Have him make sure the engine numbers match the VIN.

3. Check for oil leaks

4. Check clutch and transmission for proper operation

5. Check steering and suspension

6. Check electrical components

7. Check Air Conditioning

8. Check belts and oil hoses 

9. Check brakes for proper operation

10. Check for antifreeze leaks

11. Check OBD II for fault codes

12. Check Mass Air Flow sensor for wear and dirt accumilation

13. He should be able to itemize everything you need to put the car into street concourse condition (even if you don't want to show the car, this will give you an idea of everything the car needs). 

The list should help you decide whether you want this car and, if so, check the price range for the car.