AW is a simple way to start and it is free to get started on there and it is how the majority of booking are made anywhere in the country.
Definitely start that way.
Years ago, I and many others weren't on AW, and it was much more seedy, but things have changed.
Beyond AW, if you are going to stick with this work for more than a year, then set up your own website.
Agencies are PIMPs.
They haven't got your back.
And they won't help to schedule appointments at times that suit you they will just pass clients on to a girl who is available right then.