Years ago
http://reliabilityindex.com/ had a fantastic list of the repair costs of used cars, collected by a UK car warranty insurer. They took it down for reasons I’m not aware of but it was basically this but for used cars (and Europe-focused). It let you see repair costs per brand, model
and generation. There’d sometimes be
mad regressions in quality between the old and newer generations of the exact same car - newer isn’t always better!
It was also mildly surprising to me how badly cool cars did. Eg Porsches and Audis had insane repair costs, compared to eg similarly sized Volkswagens. I assume this had more to do with the average driving style of Porsche owners than the hardware though - but that’s equally part of the risk math you gotta do when buying a used car!
We ended up buying a 12yo used Ford Focus for 3000 euros, from a generation that had miraculously low repair costs according to the site. We had nearly no repairs on it for the 6 years after (and then it suddenly pretty much fell apart, but still). I know nothing about cars and I fully credit the site for making me not screw up.
I really miss that site so if anyone knows something similar for used car, please do share!