rust =(

SkyZ

OK, so my dads got an 02 altima, and its slowly becoming a rust bucket. how do i get rid of the rust before it spreads. is there a proper cheap way to do it? i know my dad doesnt care cuz hes says, "i'll drive it till it breaks down and get a new car" but if theres a cheap way he might consider it.

a little background info. the altima is very prone to rust (at least the 02 model) and the underbody is looking pretty bad. the catalytic convertor is probably done.
There is also some body rust because he was rear ended back when the car was 2 weeks old and i guess the body shop didnt do a good job. its clear cuz there was alignment issues with the trunk and a lot of other stuff, but yea its starting to bubble up now so i kinda want to fix all that. anybody got any answers?