I think a lot of aspiring writers who dream of making their money this way forget one thing: no matter how romantic the image of the writer sitting in a coffee shop and sipping on a Latte while writing out a chapter of their new book is, it’s still work. Hard work. And nobody is going to do it for you.
This is true for pretty much anyone self-employed.
If you’re doing this because you really want to do it (and I mean everything that comes with it) and you are really good at it (or at least are willing to put in the effort to become so): By all means, go for it.
If you are doing it because you think it’s going to be easier than a 9–5: Good luck.