Paint over Bondo

That is soooo nice. I'm sure it lasted at least long enough for him to flip the car to some unsuspecting schmuck. That being said, decent patching can be done without welding. Because some people can't afford a welder, and they are on a tight budget. Get rid of all the rust and use a fiberglass reinforced filler. That stuff is incredibly hard and strong when it cures. Before the hate mail starts, I am just saying that if one does NOT have a welder, it can work. Before I started welding body work (about 20 nears ago), that is how I did it. I have had some of that work last 12-15 years. The secret is to get rid of the rust and treat the metal.
We have a local car salesman in Gray that does stuff like that. He buys rubberized under coating by the case to cover stuff up. He's a real shiester.