Rear Main Seals can leak although can usually wait until a clutch change (and the clutches tend to go quite early).

You should research IMS failure although by 2004 most should have been sorted.

Can be heavy on suspension and brakes and all expensive to replace and you should replace them as there is no point in a Porsche which doesn't handle and stop right.

Good cars, well built but it is an 11 year old car from an expensive manufacturer so be realistic with yourself that you will probably have to spend on it at some point.