I can only speak from personal experience - our own 997 is 4 years old, had two previous owners and 21k miles on it when we purchased it and it drives like it was brand new. It was also £40k less than it cost new. 

As long as you buy from a Porsche dealer and the car has the full 2 year Porsche warranty and full service  history ( if applicable) all should be fine. 


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Porsche 997 Carrera S PDK Aqua Blue / Black - Toyota Yaris D4D  "Clockwork Rat"