If this is not just surface rust (and I doubt that it is), it would be very costly to repair - you'd be looking at welding new metal onto the panel and painting a large part of the car. If it's not /in/ the metal, you might get away with sanding it away, possibly using filler, and repainting.
For a car from 2001, the likelihood of it being an economical repair is tiny. Usually rust on the arches looks nasty, but doesn't have any huge impact to the vehicle (like, say - rusting brake pipes).
If you want it fixed primarily for looks, then bear in mind that car body work is quite a skill, and sometimes you can make things look a lot worse :-)