Here's how it worked during the Obama admin:

The gov pays the rent for anyone who qualifies for section 8.

Slum lords find an aging neighborhood and start buying up dilapidated houses with no intention of maintaining them.

They move section 8 tenants in, who at best don't know how to live like a responsible adult ... at worst are straight up criminals who steal from the neighbors and/or sell drugs out of the house.

Their unlucky neighbors, unhappy and frightened by the sudden rise in crime in their once quiet neighborhood, do the only thing they can: Move away. Then slum lords buy their houses as well.

You end up with a repeating cycle where the property values in the neighborhood plummet, letting the slum lords buy up tons of houses for cheap. You can always spot a neighborhood it's happening to because the utility poles on every corner have flyers stapled to them that read something like: "WE BY HOUSES! CASH! (xxx) xxx-xxxx"

Then they fill the houses with section 8 tenants and rake in the steady income of rent from the gov.

Within a few years a once nice, affordable neighborhood has become a horrible shithole. A suburb themed ghetto.

And cities spread into the countryside like mold. Quiet rural areas and farmland are eaten up by an ever spreading sprawl of cookie-cutter suburb developments for people to flee to. (Also the people that fled to those new developments get called racist for not wanting to live next to drug dealers or have their garage broken into every week.)

I imagine under Biden's policies it's going to be similar to this, but far worse.