[NSFW] I want to get started on Patreon and PayPal. How should I price my work?

I’m an 18-year-old virgin who writes femdom erotica for the submissive men of the world. I’m not sure how much this work is valued. Should I charge per chapter, or should I have my 200ish readers pay for a monthly subscription? I also often have chat sessions with my readers and I was hoping to charge for those too. I once read that if you’re good at something not to do it for free and I really want to make some side money doing this, but I don’t know how to start. Any advice?