One way to get affordable housing in gentrifying/fied areas is essentially to bribe developers with extras. You know, you can add 3 stories of market rate housing if you offer some essentially subsidized housing for lower income (though usually not that low) households. The other way is to allow and/or mandate that developers build "shittier" housing. Smaller units with fewer amenities. One of those amenities is parking. Parking spaces are expensive in places where land isn't cheap. If you require parking, you're going to increase the cost of the units.