The free market is perfectly willing to address this. It will do so by offering them less than minimum wage, once it is allowed to do so. Until then, "free market" is a misnomer.
Okay, so how does the "free market" address a growing underclass that can't afford to live outside poverty? How does the "free market" address social issues caused as a result of this poverty? Inconveniently, for the "free market", these people will not go quietly, and when things get really bad, violence will become an issue. So the "free market" incarcerates them, hoping they don't reproduce, unless they accept their slavery. Then afterwards, everyone is happy, living in paradise.
Why, the free market already addresses these issues: commercial prison services, commercial security forces - mostly used outside of the country of origin, for now - and bail bond companies and and and... a whole industry is based around services tailored to the growing underclass.
