I know it's pretty strict on most game jams but if someone has a busy life are they allowed to work on the game before the jam starts but still only spend 9 days like every other person?

Unfortunately all work needs to be done within the given time constraints. There are ways you can set yourself up for success, like building a template for the restrictions within the engine you're using. See the Resources page for an idea of what you can do and what assets you are given to work with.