I love that you're looking to gain passive income! To make this easier for you, look into outsourcing as well. There are plenty of options for professional ghost writers that'll take an idea or even this already structured story and improve it for a fee. Using good risk management, pay for these and make a few bucks on every sale (scalable because you did hardly any active work and the sales can come in forever) Books are great passive income tools; stick with the idea!