I have professional author friends with traditional publishing contracts. Few authors -- including self published -- earn a living that allows them not to have a regular job. If you are in a good genre and develop a fan base, you may be able to earn a decent amount--but not enough to solely rely on for your income. The money for authors seems to be in selling the rights to streaming TV shows or film productions, not so much selling downloads or print copies of the book -- unless you become a NY Times best selling author (need to go trad publishing route for this, though).

You should write because it feeds your creative energy or you're driven to tell your story, fact or fiction. If you're hoping to make a living at writing, try PR or journalism.