You make a lot of valid points in the first half there, but unfortunately to transition away from housing being an investment and towards it being an amenity, it necessarily means affecting those who choose to treat it as an investment - and frankly, all investments come with some risk. But with all your talk of "old people", I think it's fair to point out that this need not happen overnight, and there should be ample warning for retirees to divest of their investments to the private sector gamblers, for the most part.
>People who would be quickly underwater if the property market tanks deciding to jingle mail, leading to blighted streets for those who stayed.
I really don't understand this point. If it's a house where they want to live, they would just stay. If they can't afford the mortgage, yes, they can leave and buy any of the other now cheap property on the market, and the financial institution that took on the risk on lending can either sell it back to them or to someone else. If they don't live there, they're literally part of the problem of speculators treating houses as assets rather than housing, in which case they should be selling it to whoever actually wants to live there, yes.
Now as for the second part:
>As far as the state being a perfect provider to step in ... in the US about half of healthcare spending is fraud.
I feel like you choosing the only first world country with primarily privatised healthcare kind of strengthens my point, not sure what you're getting at here.
>Which land will the free or subsidized housing go on?
It shows just how badly treating housing as a capital asset rather than a public utility has corrupted how people discuss housing, that when I suggest that the government would handle any absolutely necessary rental housing, you immediately jump to low income people. And I don't blame you for thinking that, but that's basically the opposite demographic of who rental property should be for.
There's no inherent reason that low-income people should be renting rather than owning - they have no particular need for short-term housing. The only reason those two things are associated is because housing is treated as a capital asset.
Rather, the only people who have reason to rent rather than own are those who have a short term need for housing, which is going to be largely moderate-income people who move around for work, as well as students aiming for a higher-income job.
There are other systems, of course, where no one can claim physical ownership of something like land, and everyone rents - like Singapore's public housing model. Singapore's model, by the way, sidesteps the rest of your concern:
>Which land will the free or subsidized housing go on? Will the people spending a grand or two a month in property taxes want the elevated crime levels near their own front door?
Where will lower income people go? The same places everyone else goes. The only reason you have "bad" neighborhoods is because you've shoved all the economically disadvantaged people into one spot, and allowed the wealthy to cloister themselves into enclaves where the issues with poverty are out of sight and out of mind. As I said, Singapore's public housing distributes income levels much more evenly, and shows major benefits from it.