Now that I finished my first book, how long before I can quit my job?
Maybe tomorrow. Maybe never. Odds are on the never.
There are many, many authors who’ve never made enough publishing 2 or even 3 books a year to quit their “day job”. There are some (very few) who were a huge success and made scads of money on their first book. This isn’t a union. We don’t all get paid the same. Talent is a very subjective thing. Some authors are going to be loved more than others.