I would argue that nobody should own a home they don’t actually live in. All renting out does is increase the housing cost overall because nobody would ever operate at a loss or to break even. This is the issue people have with say, Blackrock who buys hundreds of homes at a time and rents them out.
Your family aren’t bad people but the business they decided to take up is inherently bad by design. If the law changed tomorrow saying all multi homes must sell to non homeowners, everyone would watch prices drop and be able to afford it.
Using homes as an investment is at its basics, exploiting a need by interpreting it as a want or practical goods. Homes are for living in. The housing industry views homes like commodities as if people have a wide choice and selection when it’s really “Omg we can afford this one that popped up randomly, we have 12 hours to decide if we want to pay 50k more to beat others away” and then lose anyway after bidding to Blackrock who pays 100k over asking.
Price of da brick going up