1. Outlaw (at the local and state level) and punitively tax (at the Federal level) short-term rentals (eg AirBnB/VRBO). The evidence that these reduce the supply of rental units is undeniable. It's not even capital intensive as people will rent units where the lease allows them to sublet short-term;
2. Start punitively taxing second homes;
3. Punitively tax ultra-luxury housing supply.
In the longer term the government should temper these market forces by creating an alternative source for housing by buying and building housing units that are rented to people on reasonable terms.