[Rainbow Six]

I envisaged more of a set up where the Service Providers (or their middle men) were just hanging around the market rather than occupying a specific stall / booth. For example:

“You need some men to work in your factory / coal mine? Go see that guy over there, the one in the black jacket standing next to (insert whatever stall name you fancy here) smoking a cigarette. Tell him what you need and he’ll take care of it.”

The prostitutes are more likely to be wandering about the market, probably approaching individuals / small groups with offers of *ahem* service. They’re likely to know a lot of people so in addition to their normal line of work could be useful contacts, trading titbits of information for food / cigarettes etc. For example

“See that guy over there with the black jacket smoking a cigarette standing next to (insert whatever stall name you fancy here)? You want to be careful around him. He provides work gangs for the factories but he’s in tight with (insert name of local strongman here). Cross him and you might find yourself down one of the mines. For good.”