so could this be resolved by having a high tax (~50%) on second/rental/investment homes?

> I will never get tired of teaching people (it's news to every single one of them!) that at any given time, there are more than 20 empty housing units in the United States for every single homeless person on the street

Are you suggesting we deport homeless people from cities with low vacancy rates, to cities with high vacancy rates?

> There is absolutely no barrier to housing every single human being beyond greed.

I suspect your answer to the question above will reveal a barrier.

A surplus of housing in Madison, WI is irrelevant to someone living and working in NYC, which has a severe housing shortage.

We are still subject to space time.

I’m curious about how these empty homes are distributed? Take California for example, where there are 19 empty homes per homeless person according to the link provided. But where are these empty homes in California? If they are disproportionately located in areas far from employment opportunities, then this suggests that we still need to build more housing near employment centers. But if there are plenty of vacancies in areas close to job centers, then this is definitely something that needs to be looked into more closely.

This is simply not correct once you account for the fact that people do not like to be uprooted from the communities they're part of. We are simply not in a post-scarcity situation for housing, and YIMBYism is essentially correct.

Homelessness is the most visible sign of a much larger systemic problem. For example, it's quite likely that many homes today are overcrowded, and people don't have as much space to live as they desire. This is bad! Not as bad as homelessness, but depending on the specifics still quite bad. The good news is that building vertically permits more private space per person, so we don't just have to accept things getting worse.

Your statement aggregates across cities with different job opportunities and economic outputs. You need to look at specific cities with housing problems, and ask whether building more houses in that specific city would alleviate housing shortages.

If this was true you should be able to build a new house for much less than the asking price for existing houses but unfortunately that is not the case either.

A lot of houses are empty simply because they are for sale. It's not unusual to take 6 months to sell.

Nobody is going to want homeless people living in it in the meantime.

Houses are also "empty" while they are undergoing renovation.

Are you ”teaching” that because some 2% of housing units are empty we don’t have a shortage? Because I don’t think any of economy, capitalist or not can reasonably obtain 100% use of any resource. 98% is pretty dang efficient and I think is actually a counterpoint to what you’re trying to argue.