I have an acquaintance who makes her living as a ghostwriter for a nicer sort of people. She routinely makes $100,000 an up for a book. She hints there are times it hasn’t worked out – the famous star who’s also crazy, that kind of thing. But for the most part, the books she ghosts are respectable.
While it’s good to have a writing niche, I’m not sure I would want to be the “go-to ghostwriter for bad guys.” Read more about “bad-boy ghostwriter” Pablo Fenjves in this Newsweek article.