The property's unleveraged income return: net operating income ÷ purchase price. Here it's the annual rent over 50 weeks (a 2-week vacancy allowance) minus rates, insurance and management, divided by the price — ignoring the mortgage.
No free per-suburb cap-rate feed exists in NZ — an area benchmark would come from a paid data provider (CoreLogic/QV) or TradeMe's official API (the OAuth follow-up). For now, sanity-check against recent comparable sales in the same suburb.