First car with low maintenance costs (up to 500€)

Hello to all, I am 20 years old and I am looking for my own car, because this month I will have my driver’s license for exactly 3 years and can therefore start with SF1/2 and I finish my training in the summer, which of course makes me better financially. Currently I regularly drive the cars of my parents, but finally want to have my own. The maintenance costs – as mentioned in the headline – should not be too high, i.e.: it should not be a car, the special it is expensive in the insurance, the fuel consumption should not exceed 10 liters in normal driving mode if possible and it should be considered an inconspicuous car. Nevertheless, it should not be too low motorized, so at least three digits, preferably between 100 and 150 hp. With the equipment I like to make compromises, if everything else is right. I don’t want to have a small car. Models that I would like are: 190 Mercedes, W124 Mercedes (probably too expensive), C LK Mercedes, 3 Series BMW (also as Coupe), Audi A4, 5 Series BMW from the 90s (probably too expensive?). I am also open to other models. Which of the models I mentioned would you most recommend to me and what should I pay attention to (what kind of motorization, typical problems etc.). Since I know hardly, I ask you in this forum and hope you can help me.