Are you sure finance wasn't the main cause?
sources: https://www.oecd.org/els/family/HM1-1-Housing-stock-and-cons... https://www.globalpropertyguide.com/pacific/new-zealand/home...
Edit: Also compare what happened to the money supply over the same period: 2011(NZD180 billion) to 2022(NZD400 billion). https://tradingeconomics.com/new-zealand/money-supply-m3