If I were king, I'd prohibit any entity or group of related entities from owning more than, say, 100 houses.
During the GFC, PE formed investment funds to snap up houses in foreclosure or pre-foreclosure. The big institutional rental home fleets started then, like Invitation Homes INVH (I recall 80K houses). During the pandemic, PE formed more such investment funds, anticipating widespread housing distress, which didn't happen but the funds bought up houses anyway - they're not going to give the money back after all. At points in the past couple of years, investors have been as much as 25% of home purchasers in many metros. Ordinary buyers cannot compete with large investors, who buy quickly with cash and raise capital much more cheaply than families. The epicenter is the South, in Atlanta 51,000 houses are owned by these institutional funds. The funds are also moving in on new home construction, with about 8% of new houses "build-to-rent"; sometimes a big fund will pre-buy an entire development.
https://hoodline.com/2024/12/over-51-000-atlanta-homes-owned-by-corporations-dominating-local-real-estate-market/
https://www.fixr.com/articles/build-to-rent-homes
Why does this matter? Well, the wealthiest own nearly all of the assets in the US (e.g. top 10% own 89% of stock market value). The only major asset class not almost completely owned by the wealthiest is single-family houses, which is still mostly owned by regular households as middle-class owner-occupants. For generations, our financial system has been deliberately set up to promote family ownership of their houses, via bank regulations and the GSEs Fannie and Freddie - otherwise the fixed-rate 30 year mortgage would not exist (and it does not exist in almost any other country). Houses are an incredible investment, in the long run, because the government keep the interest rate low, you can use big leverage, the loans are non-recourse, and the costs are tax-advantaged. And when those regular folks get old, their largest asset is usually that house, which helps them make it through retirement and leave something to thei kids. As PE and institutional investors (which are, essentially, owned by the wealthy) own more of the housing stock, the middle class' grip on their last asset class is stripped away.