Technology isn’t the hard part of OF. Money and moderation are. Most of the big payment suppliers like PayPal and credit card companies are vary about porn or outright ban it. So you need a partner who will take the money from customers and give it to you. And then you might need a different (or same) partner to give the money to the content creators.

And all the time you have to make sure that none of the creators are hosting illegal material or something that is not allowed by the money transfer providers.

But from the point of view of the creators all the money handling is the biggest service OF provides.