The Lord Mayor quite explicitly displaying his poor economic understanding.
He says that investment properties are being sold "and then becoming owner-occupied properties". He says this will drive up rental prices. Usually, the LNP likes to ignore what happens after investors choose to leave the market, because the answer doesn't work very well for them. The answer is: a renter buys and leaves the market, making it net-neutral on the rental market. It's weird that in this case he chooses to explicitly highlight the thing that defeats his argument.