An accidental killer flees to one of the cities of refuge for an indeterminate time (until the death of the kohein gadol, or even longer if the timing is unfortunate). The cities of refuge are cities given to the Levites in place of the land that other tribes get. There's a dispute in Makkot 2:8 about whether the accidental killer pays rent or lives there rent-free (the g'mara clarifies that this might be about the 6 vs the 42 cities), but even if he doesn't pay rent, he still needs food and clothing. And if he has family "back home", they need to be provided for somehow.
How did this work? Many accidental killers would presumably have been farmers, a trade they can't as easily ply in their new homes. Did they take up some other trade? Did somebody sustain them (and if so, who)? Did they beg in the streets? Did someone bring them money periodically (perhaps funds raised from their property back home)? Something else?
The mishna in 2:6 says that mothers of high priests would provide food and clothing so the exiled wouldn't pray for their sons' deaths, but that seems impractical at scale. Did the mother of the current high priest really supply all the needed food and clothing for every accidental killer in every one of the 48 cities? I understood that to be more of an occasional supplement, but that's just my own reading of it.