What's happening is the federal government is pushing small multi-family apartments (2 - 4 units) on what were previously zoned for single-family homes, low-cost apartments, and subsidizing these while fighting to get states and local governments to reduce or end zoning for single-family homes. The result of this is that developers have moved to where the money is: Small apartments on re-zoned lots. Seen a number of these now in Phoenix. In fact, people with the cash and credit are getting into this because they can just afford it and the government is heavily subsidizing it.
The problem here is the same sort of investors that caused the last housing crash are the exact same sort that are pushing us towards the next crash. In the meantime, demand for single-family housing is out-of-sight with several million units short of what the demand is nationally. In Phoenix the shortage is about 30,000 units right now or so my realtor says. That's driving the price of housing out-of-sight here.
At the same time there's too many apartments and the rent is skyrocketing because landlords are forced to raise rents on their renters to cover the cost of the empty units too.
That's happening right now. Phoenix is the 5th largest city in the US, and it is not an exception.