How to monetize adult story site?

I have a friend whose hobby is to write adult story. So far he’s been publishing his stories for free on his own free blogspot website. But when I take a look on his website it has barely any visitors since he’s bad at marketing and promoting stuff. I want to help him grow his site and share the revenue, but I’m not sure if I can manually promote or buy an ads on social media since his site is dealing with adult material. Any suggestion?