Its wild how the solution to housing costs is really just:

Build more housing. Keep law and order.

No it doesn’t need to be “affordable”. Yes rent control is a terrible idea.

Just build more housing.

Note: that the US already has plenty of housing and housing costs basically go up in areas of low crime relative to economic opportunity. If you build housing, but allow crime to rise, you have wasted everybody’s time.

New construction has already decelerated in Austin due to falling prices, which compresses already-near-zero margin on real estate development.

So yes, it really is "just build more housing." The problem is: why would you build more housing as prices fall?

If a minority has most of the wealth then the equilibrium supply may include a lot of supply of second homes, very large homes on large plots for the rich, properties sold at a premium based on how much they can extract from renters, and even investment properties occupied by nobody whilst still having insufficient small basic homes and dense housing.

Capital that could be invested in better serving the bottom half has to compete not only with the use of those resources to further enrich the rich but other investment opportunities.

There's a couple of "ifs" there and the scenario seems implausible. If I look at the prime real estate in a city it tends to be a lot of skyscrapers rather than very large homes (with occasional exceptions like say a Buckingham Palace). But it looks like the economic equilibrium is lots of cheaper apartments rather than large homes for rich people.

> ... and even investment properties occupied by nobody ...

Not much of an investment. Something is wrong if that is happening, probably manifesting as a lack of supply. Otherwise what is the point of an "asset" that doesn't generate income, degrades over time and could easily be rented out at a profit rather than sitting unused?

Whatever scenario there is where it makes sense to have an empty property, assuming a sane policy backdrop, it'd always be better for the owner do what they were going to do anyway but also rent it out.

People don't want to rent those homes out because once you're doing so it's difficult to evict a long-term tenant. You just lose out a lot on flexibility - even if you try and manage that risk by leasing out housing e.g. on a yearly basis, landlord-tenant law often overrides that since there are strong ethical reasons for not evicting someone who has since come to treat that rental space as their home.

Short term rentals are better on that score: no one sensible forms a long-term expectation that they're going to live in an Airbnb that they've rented for a few days. (If you think short-term rentals are "bad" for the long-term market or have negative side-effects on the neighborhood, then tax them to manage that tradeoff. But banning them altogether is unconscionable and just leads to houses sitting empty and unused.)