If being a superhero was cheap, everyone would do it. Sure, you might be able to pull it off if you get blessed by a wizard or recruited by the space police, but if you’re not lucky enough to acquire superpowers, having deep pockets (or a generous benefactor who does) is basically the only way to go. Gadgets, vehicles, and costumes are expensive, and it’s also awfully hard to hold down a job when you might be called away to fight crooks or angry gods at any moment. Even Superman can just barely pull that trick off.
Consequently, a significant percentage of Justice Leaguers, Teen Titans, and other DC Comics superheroes are backed by big dollars, mostly acquired the old-fashioned way: inheritance. Heck, some superheroes are even lucky enough to be born with both incredible powers beyond those of mortal men and generations of accumulated wealth.