I your Aunt and Uncle are probably lovely people. They're trying to survive in the same system we're all stuck in.
Ask yourself this, who is paying the mortgage on those properties? If the renters can afford the rent, they can afford the mortgage and then some. Your aunt and uncle, and all landlords, are collecting a premium on housing, what do they actually provide? If they're trying to save for retirement, by renting homes, who's actually paying for their retirement? Will those people be about to afford to retire if they're spending so much on rent? They'll end up with nothing when they leave. Your aunt and uncle will still have 3 to 5 extra properties.
They own suburban townhomes, in some cases you find a renter who'd rather not own a home. In most cases, the market has progressed to a point where home ownership is impossible because people are hoarding homes and withholding access for rent.
It's an unethical system. Your aunt and uncle are small line landlords and a symptom of a larger problem. They're participating in an unethical system to gain an advantage, and it's hard to blame them for that. That doesn't make it ethical, or good.
Jefferson said he "participated in a broken system that he hated." In reference to slavery. He actively tried to reform that system and was rebuffed. He's still seen as a slave holding landed gentry today, and it remains a black spot on his (admittedly spotty) legacy. How are the people who owned 3 to 5 slaves different from those who owned 50? How are they compared to those who could afford and benefit to own slaves, and still advocated for abolition?