That's what's usually known as risk. They invested in an asset to provide their livelihood, that form of income has a set of risks associated with it, just like having a job carries a risk of losing it or how investing in securities carries its own risk.

How much are we willing to protect the investor from risk, in this particular case, at the potential expense of a tenant's ability to have shelter? Obviously we need some form of balance but the finer details of it are wildly arguable.

So you're suggesting that because they have the ability to buy additional housing and charge people to use it, someone else should bear the risk?

All investments carry risk.