I believe renting is the weakest part of my idea, but I don't see why it can't be solved.
Maybe humans are allowed to own some maximum number of properties for the purposes of renting it out, and that number will decrease over time.
Maybe banks can own houses and rent them out at some capped amount.
Maybe the government can own houses and rent them out with the express purpose of "rent to own", with absolutely no intention of "earning a profit".
I don't have all the answers, but I think it's pretty clear that companies owning 40% of ALL residental homes in a city and making massive profit renting them out does not make housing affordable, and it does not allow people to have their basic human needs met. Therefore something needs to change.
do you have a reference for that 40% number. I have a hard time believing it is accurate, and especially not for single family homes. It looks like large companies own 2% of single family homes in my state of California. This reference puts the number at 3% of single family homes nation wide
being institutionally owned, or 446,000 out of 15,1 million homes [Ref 1, pg 9].
There is also a fundamental tension between forces driving people into dense urban apartments and the desire for home ownership. When you look at dense European cities, virtually nobody owns their flat.
Overall, Im not opposed to banning mega investors, but think it will just make more opportunity for small scale rental companies. This reference [2], talks about some of the laws proposed in California, but also has a lot of valuable context.