There was a Chinese restaurant here in Nevada, actually a couple owned by the same woman. They were sort of the typical dine and dash $7 combo plate kind of places.
This was years ago when I used to deliver for a produce supplier.
Anyway, she always had a kitchen full of workers. 5-8 at anytime in a small kitchen, working away. None of them spoke a word of English. I thought it was strange and wondered how she could possibly be making money with that sort of labor. It finally dawned on me....as the entire would switch out ever 6-8 months, that they were probably not being paid. I figured they were working off debts to get here.
Massage places seem to be the places doing this sort of crap now. I have noticed a bunch of the little strip mall, shady looking massage joints spring up around town. Like 8-10 or so in a row of only 200,000.