Do you have your own adult website on the side? Did you try it? You can build one and just keep adding new posts every day while writing for others since it does not require that much time.
If you are new, then you have to build up some portfolio and get some clients first for a cheaper fee, get as many small gigs as possible and once you build up your reputation, you will get more job from recurring clients that you will build trust with and you will be able to command higher fees.
At the end of the day, there are still all kinds of webmasters looking for writers, on this and other adult forums, so you should not have big issues with finding new people to work with, if you are affordable and can deliver good work.