Make sure to check over the sills and arches for any corrosion, make sure cambelt + waterpump have been done, if it's DSG make sure it's had the oil and filter changed every 40k, make sure it sits at 90 degrees when warm (new thermostat needed if it doesn't), try and have a quick scan underneath around the wishbone area to see if the bushes are perished. Then just check the usual.. oil leaks/damp patches in the engine bay etc. They are at the age now where lots of problems can start to arise if it hasn't been well cared for!