Financial and familial resources. If you are middle and upper middle class you are more likely to own your home rather than rent, have better credit, have access to more lines of credit, have more saved up, have actual retirement accounts, have more assets you can liquidate, have a job with pto and medical leave, have a salary rather than hourly pay, have flexibility with your work and still get paid, only have one parent working etc. Not only do you have that, members of your family also have that.
Do give you an example: my wife and I are from middle to upper middle class families. All 4 parents worked but worked well paying jobs. Our parents paid for us to go to Clemson. We never had to worry about loans. We never had to work in college. When we moved our parents helped us with the move physically and financially. When we bought a place her parents gave us some money to cover the savings we had to liquidate. They gave us money to help us with renovations when we bought our second place. When a grandparent died we inherited a bunch of stocks that we can liquidate if need be. We both have salaried jobs with a lot of flexibility, good pto, and very good healthcare.
If we ever had a significant crisis I wouldn’t be worried about running out of money
