How much rust can be handled when buying used cars

Hey, I wanted to get this car as my first car, but my parents put a dash through my head and gave me a Corsa. Now it’s finally time to catch up with my dream and after I had it really grinded in the last few years, I’ve been really busy with this car lately. I found a lot about the rust problems and therefore a question for you: How much rust is manageable with the NB? It’s already over when I discover rust bubbles at the bike runs, because then I have to replace the entire bike run? Quite apart from whether the money that I would put in the car was in the end economically total grütze. I want exactly this model and I want to make exactly this chic. However, if I buy a car for 3-4 thousand €, I don’t like to hit another half on top of it for a complete rust removal of the problem. ielleicht only so extremely bad before with the rust? Need urgent advice :,) Greetings, Lucas