Mr Patten said sharing a mortgage has its appeal for many looking to get into the property market. "They get to stay in the area and buy a nice house together."
He added once they have reduced their debt they can sell and buy a new house on any capital gain.
One of Mr Patten's clients, a 29-year-old teacher, was in the process of doing just that, having just bought a $890,000 three-bedroom house, in South Auckland, with his 23-year-old partner and another couple.
The teacher said it was go halves, or wait another few years to get into the market.
"We would have needed to save for longer, but the market was only going to go higher."
He admitted there was an element of trust.
But the teacher added they have employed lawyers and drafted agreements that set out all the terms of the deal.
Andrew King, of the New Zealand Property Investors Federation, said sharing a mortgage had its fair share of risks and benefits.
"At this point prices are going up faster than people can save, so it is a good way of getting into the market.
"But, even if you are sharing the mortgage, you are still liable for all of it."
Ashley Church, chief executive at the Property Institute of New Zealand, cautioned anyone looking to share a mortgage with friends.
"It's a good idea in principle, but there is nothing more sure to divide friends than dollars."
