I sold my mk5 back in 2009 so I'm a bit behind the times, however around about then it was decided by VW to reduce the cambelt change intervals to 4 years from memory. They may have changed the policy again since then. There was a lot of fuss about it at the time on here, I remember that much!
I got a cambelt and water pump change done in early 2009 and ended up trading to a mk6 later that year. Mine was about four years old and had about 50k on it I think. It may have had less miles, it's a long time ago.
There will be loads of archive info on here but it would be just as easy to ring VW locally and ask for current recommendations and prices to give you a bargaining lever on the purchase of the car.