As Auckland's median rent rises, renters say some people are overfilling apartments.
In its latest report, TradeMe said even the smallest units in the city cost upwards of $400 a week, and that prices overall are up over 8 percent from a year ago.
TradeMe said the median price for a one-bedroom property in Auckland is $413, rising to $550 for a three to four bedroomed place.
That compares to $285 for a one-bedroom flat for the rest of New Zealand.
Sean Moidra lives in Auckland's Greenlane, and said renters, especially students in the city centre, were resorting to desperate measures, cramming as many people into apartments as possible, even if just to make the rent affordable.
Trade Me Property head Nigel Jeffries said asking rents in Auckland had "rocketed up" over the past year.
"You're now looking at $499 per week for a typical property, taking annual rent costs close to $26,000 - about $2,000 more than a year ago. It piles more pressure onto the cost of living for tenants," Mr Jeffries said.
Trade Me said the median rent in Christchurch had dropped almost 5 percent in the past year, as prices cooled after the rush for post-quake housing.
"The Christchurch rental market was extremely hot two years ago, with asking rents rising more than 13 per cent year-on-year," Mr Jeffries said.
"In March this year it peaked at a weekly rent of $495 to surpass Auckland, but across the remainder of 2015 we've seen rents ease right back and Christchurch tenants are now being asked to pay $3,400 less a year."
No real changes were reported for Wellington, but Trade Me said rents in the regions followed employment opportunities, with prices dropping in Gisborne and rising in the Manawatu-Wanganui area.