Find a patron.
Sometimes that patron will be a publisher or a royalty check.
Most likely, however, your patron will be your day job, your generous parents who let you live with them, or your spouse.
In my case, my patron is my supportive (literally) husband. He finances my hours of writing with his own income, and he does it joyfully. Is it tight living off of one income? Sure, but his willingness to let me stay home and write for the benefit of my neighbor – good return or no – is what makes authorship possible in our house.
That is why I joke with him that he is my patron saint.
(Yeah, he doesn’t like it when I call him that.)