If your goal is to make enough money to retire early, prioritize earning potential over job satisfaction, since you plan on getting out of the rat race early, anyway. Consider the types of jobs that pay extraordinarily well in exchange for hard work, little psychological satisfaction, and a punishing lifestyle, such as investment banking, sales, and engineering. If you can keep your expenses low and do this for about 10 years, you can save a nest egg for a modest but youthful retirement, or to supplement your income while you do something you really love doing but doesn't pay much. But keep in mind that delayed gratification requires clear goal-setting and strong willpower.
I surprisingly get a lot of people asking to detail their car. I never intend to make a business of it, but I love doing it to my cars and people ask me to do it to theirs. All it takes is a cheap orbital buffer (mines a used craftsman) and a shop vac. I normally get easily $100 for a basic wash/wax/vac, or $200 to remove scratches and polish then wax the car.
If you’ve got some free time and don’t live in the middle of nowhere, becoming a Lyft driver can be a very lucrative side hustle that allows you make money fast. And right now, they’ve got a promotion going on where any new driver will instantly get a $300 bonus after completing their 100th ride. If you start now and hustle hard on the weekends, you can probably unlock that bonus within a few weeks of driving (and that’s in addition to your normal earnings).