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This sets a price cap, makes these high density spaces affordable for people who want to live their whole lives there and not just their single 20's, brings diversity into communities and drops the floor out of the prices on these single occupancy closets going for $2000 per month.
Office buildings sit mostly empty for the same reason.
Tax the owners to punish the bad bets and eternal growth expectations of banks to force them to use the space to the benefit of the community or be forced to sell when they run out of money. Use zoning laws to prevent the destruction of units to avoid taxes.
Percentage return on investment has nothing to do with the basis. Investors will have to serve a lot more people to get the same absolute return. The percentage return won't change all that much for actually building and operating. The year over year growth in valuation and rent is what needs to go (buildings go through several sets of hands over the first decade or so anyway).
The US Federal Housing and Urban Development Department was intimately involved in the Savings and Loan collapse of the late 1980s. It was punted around and repeated in the 1990s, but the stock market gains of the late 1990s diluted the news in public. That phase culminated with a dot-com bubble collapse and ultimately, the 2007 dollar credit crisis. Leveraged purchases of real estate were part of that financial soup. Many of the players from that time were "boomers" and their seniors, so living memory of those circumstances are now fading. There are many, many non-fiction books about these topics.