There is something interesting about your premise, but be warned – there are very few films about screenwriters that ever get made. Why? Probably because very few people can identify with the struggles of a screenwriter. Most people hardly even know what we do exactly.

Having said that, if you do go through with this story, I would suggest introducing a strong inciting incident. Maybe something like Jumanji or Beatlejuice, e.g., your struggling horror writer could organize a seance in the old house. That would make them a more active hero. The ghost/s turn up, the writer gets his inspiration for a million-dollar story, but now the ghosts turn on him, and he can only reap his reward if he can escape the ghosts and get out of the house.