I've once talked to a semi-successful author. His day job was Mechanical Engineering at the local university. He eventually quit once he had his formula worked out.
He writes crime novels. Doesn't even like them, but if you want to sell, you either write smut (big gamble) or crime novels (less crowded). Anything you actually want to write about, you have to shoehorn into the crime novel. You also have to keep your protagonists whether you like them or not, or else every book will be your first one.
He also found that he had to write local novels that take place around the local tourist sights. He couldn't write about his actual hometown of course, but there is a touristy spot an hour's drive from him, so that's where the detective had to be based for every single adventure. The touristy area must also be a city. That way you have half a million inhabitants, and the same amount of tourists whose relatives are looking for gifts.
He was basically playing bookstore SEO.
Unsurprisingly, being an ME, he had a product lifecycle. He was working on several books at once in a pipelined fashion. One was being drafted, the next one was being written, the third one was in early proof reading, the fourth one was being finalized. That way he had a good balance between creative and menial work at all times. He also explained how he was careful to use few proofreaders in the early stages, because apparently, his work is a dire read before any corrections. He has a process where he rotates through his early stage proofreaders, and mostly gives them later stage work that is more readable.
Being a successful author is no more romantic than being a successful programmer. Or painter. Or mathematician. Any romanticism is at odds with professionalism, e.g. what works. And that's the same across all these professions.