In the red light district the clients walk past the windows, behind which the sexworkers are seated. You can rent a room/window from an owner. The owner of the rooms checks if you have the legal age of 21, if you are legally allowed to work in The Netherlands and if you do this work voluntarily.
Behind the window you are self-employed. You decide who you let inside, how much you charge, how many hours you work and what kind of services you provide. That also means that you can always refuse a client.
Sometimes there are hostesses/hosts. They take care of the cleaning, providing you with clean towels and sell condoms.