Hierarchies need hierarchy. Economic apartheid is one of the most common - and least questioned - ways to enforce hierarchy.
It's the usual problem of defining the difference between a progressive and a regressive economy. Regressive economies claim to be about "freedom" but in practice it's a very selective freedom that benefits a few small sectors and acts as a brake on innovation, development, and entrepreneurship for everyone else.
Consider all the businesses that could have been started by talented people currently spending all of their income on rent. It's a brittle, oppressive outcome.
Progressive economies rely on wealth redistribution to create something closer to a genuine meritocracy.
There's a whole PR industry devoted to denying this, but it's not a coincidence that the US was a powerhouse of innovation when redistributive taxes were at their highest. And has stagnated as economic apartheid has become more entrenched.
That's the crux of the political debates going on today. What kinds of values are represented by the status quo, and what kinds of values may replace a (retrospectively) naive approach to meritocracy.
Accountability on the part of the prospective owner can be achieved in multiple ways, but using down payments probably minimizes the amount of bureaucracy and following-up in how authorities manage this kind of thing.
Of course, implementing it this way creates "structural inequity", i.e., a process that inherently separates one group into two groups along lines that members of that group have little to no control over. Obviously the property not-having-money is correlated with other factors such as skin color and whether your parents went to college, which creates divisions along lines that are not just economic but socio-economic, and influence the development of not just that person but also everyone who depends on that person, including future generations.
I would be very interested to hear more from systems theorists on other kinds of methods that don't reproduce these kinds of correlated outcomes.