It depends. The market for porno fiction is quite niche and often faces legal and ethical restrictions. So, in general, it's not a mainstream area that sells well.
Online horror magazines like Nightmare Magazine or Apex Magazine are also good places for new writers. They accept submissions of horror flash fiction. Although the competition can be tough, getting published in one of these magazines can be a huge boost for your writing career. It gives you credibility and exposure in the horror writing world.
Writers get story ideas from all kinds of places. Some draw inspiration from their own lives and experiences, while others might get ideas from reading other books, watching movies, or observing the world around them.
Goodreads is mainly known as a book - review platform, but it can also be a place to sell your novel ideas. You can start discussions about the type of novel you want to write, share some of your initial ideas, and engage with the community. There are also some industry professionals who are active on Goodreads, and they might be interested in your ideas.