Our advances are only a few thousand dollars. They can help you buy a piece of equipment or software you need to write the book, but they won't allow you to take a lot of time off from work. On rare occasions we pay authors to take time off and complete a hot book. But usually, you have to find extra time to write. Forcing yourself to sit down and write, week after week, is the hardest part of the authoring process.
Many authors get up two hours earlier than usual and find a quiet place to write.
You may find time in other ways, but be sure to set some aside every week. Not a choice I would recommend. In both cases it caused a lot of stress as they rushed to get their final drafts to production. We try to let authors write with any tool they like. But we have to find a way to translate your format into one we can use.