I am buying a 2003 A4 Avant 3.0L Quattro with only 24,000 miles.
When do I change the timing belt? @ the mileage point or is the age a factor?
Thanks

 

Damn, that's low mileage. The Timing belt interval is Audi recommended at 90k miles, most Audi guys do it between 75-85k miles. You might want to check the belt since is already 7 years old though, open the little cover with a torx screwdriver and look at the belt, if it looks a little too worn or there's cracks present is probably time for a new one.

 

I would just replace it in the near future, that belt just won't last that long, even with only 24k on the clock. If the belt breaks you're looking at a repair bill between $3,000-$6,000 from bent valves/dinged pistons.