i would say the worst of it would be the frame rail. It looks like some pretty deep rust has formed. The colour on it shows that. But its not that bad. If it were to be grinded or sandblasted there would be a hole. Its saftieable and a really easy quick fix. Por 15 that rust!
Not trying to hinder the sale. the frame is in good condition for an s13. My first s13 was way worse and i drove it for like 2 years lmao