It’s well known that artists are likely to starve until they become successful. But I bet you didn’t know that the majority of writers who aren’t in journalism have a day job. With the exception of Stephen King (who shall be named the messiah of the modern novel), most novelists are also professors. So don’t count out the possibility that you will still have to keep a full time job when you publish your first novel.
A good example of this phenomenon are two of my professors who both have published several commercial novels. One of them is becoming wildly successful at his work, and yet he still chooses to have a university position. Go figure!