"It just takes one not to sell for the value they thought [they were going to get]."
He said people tended to ask the bank how much they could borrow, not how much they should borrow, and then go out and shop.
"So the minute you don't get your number you have got a challenge."
Collins said that meant it was getting tougher for those looking to upgrade their home.
He said part of the challenge was banks constantly changing how much they were prepared to lend.
"It depends on the week - it is a week to week thing.
"Normally we would get changes once every six months. Now one bank is changing something every week."
He said that could be their rates, serviceability criteria or their take on responsible lending.
Collins said one example was more over-55s being turned down for loans.
"If the lending is going to be significant over the age of 65 they are being turned down or need to show they can pay it back by using KiwiSaver or downsizing."
Collins said there had been a change in view from buyers in Auckland from "I have got to just get on the ladder" to "I can wait".
People were also putting in cheekier offers, he said.
Six months ago sellers had expected offers to be $30,000 or $40,000 more than the asking price.
But in one recent case a seller had agreed to just $5k over their asking price.
Collins said building inspectors were also seeing much lower demand for their reports.
At the peak 30 people might want an inspection done on a house - now they may only get one or two people.
He said buyers didn't want to get an inspection until they were sure they were going to buy now.
The change was opening up opportunities for cash buyers and first home buyers who didn't have to sell first, he said.