I sell erotic stories online through Amazon Kindle. Made more than $200K last year but it's hard on the imagination
Passive income is defined as high upfront work and very low maintenance work. Other than possible marketing tasks the author's job is done once the book is published and collects money on every sale.
Authoring a book, sure. But the parent poster implied that he/she continuously writes these stories, i.e. many of them, hence why they said it is "hard on the imagination".
I mean I'm still getting paid for the features I wrote for my company's software two years ago!
How many pieces did you have to produce to make 50k?