Taxing empty properties might help a bit. But it doesn't address the root of the problem. That housing has become such a scarce resource it can be treated as a commodity. We have the technology to build denser and higher. There's no economic reason that housing should cost much more than the cost of construction. Which should only get cheaper with time, as technology improves. Certainly not more expensive.

But this doesn't happen. Why? Because the people commoditizing homes want to protect their investment. The scarcer housing is, the more money they make. It's an incredibly perverse system. It hurts the poor especially. Even the middle class ends up losing most of their income to it. It leads cities to stagnate instead of grow.