I think if you look closely it was just hidden behind various structures, like e.g. hiring seasonal workers from abroad, housing them in your own (substandard)

I think if you look closely it was just hidden behind various structures, like e.g. hiring seasonal workers from abroad, housing them in your own (substandard) buildings, and cutting their wages by the amount of rent that you charge so their take-home is well below minimum wage. But they tolerate it because it's still better pay than they can get in their home country.