The Take-Home
Experience of the previous generation supports the following recommendations to apprentice writers:
Novelists, even successful ones, have jobs. Most have professional degrees. Most work at jobs that involve writing. So, start a career, or at least get a marketable skill.
People who write literary fiction generally teach at universities, get fellowships, and publish with academic or specialty presses. So, if you want to write literary fiction, get an M.F.A. or a Ph.D.
You have to be mature as a person and a writer to handle publication of your first novel. If it doesn't sell up to the publisher's expectations, you're likely to get dumped, and may have just as hard a time finding another publisher. On the other hand, if your first is successful, the publisher will probably press you to stay with the same characters or genre, meaning you had better like what you're doing a lot. So, don’t be in too much of a hurry to publish your first novel.
People who publish frequently write works commercial publishers consider marketable. So, if you want to make money from novels, pick a genre and get a series going.
Almost all these novelists had other outlets for their creativity and/or sources of income. They also wrote stories, poetry, journalism, scripts, computer games, advertising, etc. So, cultivate versatility.
The Internet is changing publishing and the way all creative work is promoted/distributed. This can only be a hopeful development for novelists, because traditional publishing ceased to work for all but a lucky few of them a generation ago. So, waste no time mourning the decline of traditional publishing. Look for new opportunities.