There is so much to research and so much to learn about publishing and self publishing, etc.
Income could be low or non-existent.
I haven’t actually done it, so I can’t tell you how to do it.
I have the outlines of about 5 books I want to write, but I’ve been too busy with my part-time clinical practices, locum tenens, file review, expert witness, and managing my investments to write.
I’d recommend picking one path, say locums and write a book.
I’d recommend to make sure your finances are all in order, unless maybe you have no children or your spouse has a lucrative job.
All I know is, it is much easier to say you are going to write a book than to actually write a book.