On the old warrior forum there were WSOs (aka info products sold on a special thread) about how to sell WSOs. Since WSOs themselves are about how to make money, they were selling a book on how to make money by selling books on how to make money!
I have a book called "The Art of Self-Promotion for Musicians" by someone who quit being a musician to write such books.
There was once a one-day course in my city about how to make money as a jazz musician, but I couldn't afford to go. (I think it was $10 or $20.)
I have a book called "Ideas Generation: Tools for Being Constantly Fresh, Creative and Original" by Rosemary Herceg, Tim Flattery. (2000) I will never forget reading that Rosemary Herceg had been caught repeatedly plagiarising most of her monthly magazine column from a column in another country.
(Now years later when I google it, hardly a single mention! Huh? She's now apparently some kind of business/ad guru.. I can't help thinking she had that story erased from google. It was outrageous. She seems to have blamed a photographic memory!