In order to be allowed to build housing in much of America, it is required that some portion of the units sold must be "affordable" housing. This is justified on the grounds that otherwise, the only housing which will be built will be luxury apartments, unaffordable to anyone but the rich. Rich consumers will get housing, while poor residents will only end up displaced out of their homes.
Rich consumers will get housing, while poor residents will only end up displaced out of their homes. All housing is housing. In fact, in some sense all goods are other goods, because they all trade off against a consumer's budget constraint.
In fact, in some sense all goods are other goods, because they all trade off against a consumer's budget constraint. When a developer builds luxury apartments, it diverts high income consumers away from other, lower-quality housing, which in turn diverts others, until eventually it has filtered down to the lower classes.