If you do a few calculations, the gross return on a rental in Auckland for example, is about 5%. After rates, insurance, water, and maintenance (no management fees included) the return is about 3.5%. You can get over 5% at the bank. (All before tax)
Doesn't stack up. ONe of 2 things has to happen, a fall in house prices, or a long period of stagnation as rents catch up.