Unethical? Should be disallowed period. I do strongly believe that once a propery is yours what you do with it is your concern and nobody else's. However, the business practice of purchasing properties to profit from selling it again in the future should not be allowed. So, what should happen is the government should not allow the transfer of ownership when the seller has a) multiple properties and b) is selling a propery for more than 3% (inflation adjusted) of the intial purchase value. I am all for living in a house and selling it at a ridiculous profit though so long as that is your only property.
With the exception of employee housing, any non-individual entity including agents of corporations should not be allowed to purchase even one residential property.
With the exception of diplomats, foreign citizens should not be allowed to purchase more than one property.
These laws should be applied in any developed country.
This is one of the reasons they wanted corporations to have rights as a person, because in regular reasoning a corporation owning houses, making speeches and donating to parties makes no sense as their activity and existence is entirely in the sphere of privileges not rights.