As MongooseGa said, the rot that has started eating the body will cause issues.
I myself don't like rust and really wasn't used to dealing with a lot of it living in Oklahoma.
Purchased an LX in August that had some rust concerns on the under carriage. Bought in Oklahoma but the vehicle lived in Illinois for several years. No frame rot and no body damage, i.e. bubbling anywhere. One thing I noticed was that all of the weep holes had an oily residue around them, meaning someone actually correctly applied some sort of rust preventative on the inside of the body panels. My only concern at that point was the undercarriage and surface rust therein. I could tell that the rust I had to deal with wasn't a deal breaker for me and I knew I didn't have internal rot taking place. Point is, you can tell if someone was trying to care for the vehicle in order to keep the rust at bay. If the correct preventative measures are taken and surface rust is your biggest enemy, join the club. These vehicles are prone to it. If you're willing to put in the time and effort, you can work out the surface rust problems.
IF you purchase a vehicle with surface rust and decide to take care of it, my advice is to brush it off and spray a rust inhibitor on it. Either leave the rust inhibitor or go over the inhibitor with a paint. DO NOT use a rubber coating if you're not sure you have all of the residue "active" rust off. Last thing you want it to trap it and cover it while it continues to eat away.