New research from banking analysts Digital Finance Analytics (DFA) found the percentage of investors with more than five properties in the ACT has nearly doubled in the past year.

The figures come as Treasurer Joe Hockey denied that housing was becoming unaffordable, saying that first home buyers can break into the market if they "get a good job that pays good money".

Matt and Rebecca Hein, both 32, know first hand how hard it is to buy property in Canberra, after moving into Ms Hein's childhood bedroom and putting off having children to save up for their new under $500,000 home in Moncrieff.

"We're currently living in my first bedroom, It is not conducive to having a family right now," Ms Hein said.

Mr Hein said they needed to quit their rental home in order to buy one of their own.

"Ninety per cent of our stuff is in a storage shed, It's been a financial decision," Mr Hein said.

Although Canberra is more affordable than many other capital cities, the proportion of the market taken up by investors rather than owner-occupiers is on the rise, leaving would-be residents outbid by investors.

In April 2014, 11.6 per cent of investors in the ACT had more than five properties, according to DFA's household survey.

A year later in April, DFA found 20.8 per cent of ACT property investors had more than five properties.

The number of property investors has also increased by nearly 28 per cent within the 12 month period to April 2015, according to the same data.

Meanwhile, Canberra has recorded consecutive quarters of house price growth in 2015, with half of the 10 most affordable suburbs in which to buy growing in the past 12 months, according to Domain Group data.

Prices for houses in Canberra's cheapest suburb, Charnwood, rose by 1.3 per cent in the 12 months to April from a median price of $395,000 last year to $400,000 this year.

In the fourth cheapest suburb, Ngunnawal, prices rose 7 per cent in 12 months, from a median price of $400,000 to $428,000 this year.

Marc Roland, chairman of the residential section of the ACT Master Builders Association, said many of his clients were "stressing out".

"Unless there is a correction of some kind in 20 years' time there will be people who own houses and people who don't; buyers or renters. You will be one or the other," he said.

In Canberra, median house prices were five times median incomes, up from about three times median incomes in the 1990s, former head of policy development in the ACT Treasury, Khalid Ahmed said in May.

But the capital has it better than most.

The ACT remains the most affordable state or territory in which to buy a home or rent because it has the highest median weekly family income of all capital cities.

Canberra's year-on-year price growth of 4.2 per cent is well behind Sydney's 16 per cent.

The Real Estate Institute of Australia and Adelaide Bank Housing Affordability report for the March quarter found just 19.7 per cent of a weekly income of $2521 was required to pay the average loan.

In the second most affordable jurisdiction, the Northern Territory, home owners pay about a quarter of their median weekly family income of $1927 for the average home loan.

Housing Industry Association chief economist Harley Dale said while it was possible the territory could experience a property price boom, current economic conditions did not support it.

The territory last experienced a price boom in the early 2000s when annual median house price growth peaked at 32 per cent in mid-2003.

Mr Dale said current record low interest rates had been countering negative economic conditions and that's "why we're getting 2.4 per cent growth not 12.4 per cent growth".

First home owner grants in the ACT fell to their lowest number in 10 years because the ACT government restricted the grant to buyers of new homes. They then cut it back in this year's budget.

ACT Chief Minister Andrew Barr said Canberra was not like Sydney or Melbourne and "affordability has been improving".