Okay, I can ignore things like the car doesn't look nice or doors don't lock. But what should I actually look for? What are the things I shouldn't compromise about? Is there some useful metric to calculate useful life of the car? Rules of thumb for issues that may arise, like bad brakes, tires, engine noise, etc? What are things I can fix myself?
My point was this is cultural knowledge among blue-collar circles. My other posts were about things I learned about white-collar circles.
To try to answer your questions: I don't think there's any useful metric. Unfortunately, you never know how long a car will last. It just lasts until it's giving you a lot of trouble. The things you can fix yourself are depends more on your willingness to spend time + money on parts, not just mechanics. I'd say my family personally stop a bit earlier than some because we're not ourselves mechanics as a side hobby. The answer is different for every person. :)