I’ve been there and done that. Though it’s only possible if you have absolutely no responsibilities at the time and have enough cash saved up to just sit around writing all day for a month minimum. Though you’d have to work at it as if it was a full-time job — one that you most likely won’t be paid for anytime soon, if at all — to actually finish it in a month like I did.
It was fun and I’d do it all over again, but I wouldn’t say it’s worth it on a practical/financial level because you quickly realize that writing a book is actually a lot easier than getting it published. Especially if your literary ideal is something really niche and crazy (and unmarketable) like avant-garde postmodern literature, like mine is.
Though I wouldn’t really call myself a “practical” person in general.