David Farland discusses L. Ron Hubbard's writing essay, "Manuscript Factory" and how it was an eye-opener for him. His instructors in college had been hobby-writers and didn't write to make a living. He used this advice to help build his very successful career as a writer with his own manuscript factory.
You can read this and several other essays, along with 13 videos featuring David Farland, Orson Scott Card, and Tim Powers in "L. Ron Hubbard's Writers of the Future Online Workshop" available for free here: https://www.writersofthefuture.com/writing-workshop/
Writers of the Future Podcast