priming my car, have a couple questions
 

Ok my car has needed a paintjob for a while now, the paint has chipped off in a number of places but I don't have the money to get it painted quite yet.

I want to prevent any more rust so my question is this..... if I sand down the car and use a waterproof primer will it hold up? I'm sick of looking at the rust spots and really don't want it to get any worse.

any suggestions on choices of primer?

thanks for any help

Just make sure that the primer really is water proof.