It's largely illegal to build units that are sufficiently small to be affordable. Zoning requirements in most places have square foot minimums and amenity requi

It's largely illegal to build units that are sufficiently small to be affordable. Zoning requirements in most places have square foot minimums and amenity requirements (such as parking). That said, even "luxury apartments" give the wealthy a place to live rather than bidding on existing housing stock, and so do relieve price pressure on older buildings.