Managed my friends only fans for a bit, we got her account to top 4.5%. She brought in ~$1.5K on a good month. One time we got up to $2K. This is with her having done porn with a few big studios and having a decent amount of followers on Twitter. There is no Discovery feature or feed on OF, you have to direct them there through a direct link. Had to keep a consistent production schedule, deal with inquires from patrons. Successfully running and only fans is like running a business, people don't simply give you money.