That is true in the same way that Ubuntu is Debian. I prefer the base version where I can choose what’s necessary for me for resource management and troubleshooting purposes. I forget what it was, but there were a few issues where Endeavouros was not working properly and the Arch wiki solutions did not work for it, could have been my error as well at the time.

I am not an expert by any means, but depending on the mileage on the car and how much life you expect to get out of it, I feel that taking care of the rust now will be better sooner than later. My guess for price would be 1000 max, anything over that you should consider holding off on and using the car until you can’t anymore, maintaining the basics (oils, tires, brakes, fluids, etc) and putting the money towards another vehicle or down payment if possible.