Read recent news about arrests made in HK of buildings with 1 on 1 apparently in an "abandoned" building.
Looks like mm who are in HK illegally or overstayed, as well as "drivers" to get the customers in. Seems like those guys got a hefty cut on commissions.
So as long as mm is working by herself 1 on 1 as a legal resident of HK and probably with a license to operate, it is perfectly fine.
But the tourists mm and the men or women hustling for customers can all be arrested for their work.
In a way, similar to the condition in Canada.