I think the issue is rooted in extraction of value vs. contribution of value, I believe that an individual should not own more than they can contribute value to.

If the landlord personally contributes value by maintaining the houses and charges fair rates, and the tenants benefit from not owning their houses, then that is not an exploitative relationship.

Where I have seen renting become unethical is when landlords own so many properties that they must hire third-parties to manage their properties for them. In such a case the landlord is unable to contribute value to all their properties and tenants, so therefore he owns too much.

Another way landlording becomes unethical is when rent is raised unnecessarily: e.g. Trailer Park Millionaires. In such a case the landlord does not need more income, but they raise rates anyway to earn greater profit. That video is a pretty egregious example of investors buying trailer parks so they can raise rent to turn a greater profit, the investors have no interest in trailer parks other than profit. The tenants who live in those trailer parks obviously suffer, so this is unethical.

It’s ultimately less about the formal arrangements and more about the informal relationships between people. Is the landlord screwing over their tenants, and extracting more value than they contribute? That’s unethical. Is the landlord fairly contributing value and making their tenants lives easier? That’s not unethical. How you define “screwing over” and “fairly contributing” can answer whether or not your situation is ethical. Are they renting to you just to make a profit, or are they renting to your family for your family’s benefit as well?