after the winter my rockers were basically non-existant. We cut off the rest of the corroded metal then brushed and rust treated the whole area. Since i have no welding abilities we got ghetto and riveted sheet metal in to form the rockers. Everything was undercoated in the process and after. I have since covered it with sideskirts but im happy with the results. For a car that may only last/be in my possession for not even another year, its fine. But you probably care how your car looks..
Only costed me like 10-20 for the paint. No before pics but this is a finished side. Bottom of the fender was also destroyed and repaired
EDIT: Just noticed what section this is in. Not offereing to fix it, just giving an idea. My bad, delete post if needed