Another alternative is to save aggressively working at a lucrative job when you're young, then do the startup when you're thirty-five or forty and can live, with discipline, on the gains from your investments. I know at least one very successful person who took this approach (anecdote != data, I know). Not always an option depending on your credentials, but there's something to be said for a hybrid approach of building a personal runway (and gaining skill at the craft) before quitting and throwing the dice.
Obviously you shouldn't do anything to shorten your personal runway if you plan to make a startup. Big houses and mortgages and expensive cars are out, even if you don't plan on quitting immediately.
Some of my bias may be showing here, because I'm fairly satisfied with my life and work at BigCo right now.