Joanna Karalis and her daughter. The mother of five has paid up to 50 per cent of her income a week in rent to live in Sydney. Credit:Nick Moir The figures, obtained for Fairfax Media by the Australian Bureau of Statistics, count the number of usual residents year-round, not just those home on census night, with a large proportion aged 65 and over. "These people are cruising through their senior years but they are sitting on a huge amount of unused real estate," Mr Pawson said. Seniors are discouraged from downsizing by state government stamp duties that cost homebuyers tens of thousands of dollars, and inject billions into the NSW and Victorian budgets each year. In Victoria, pensioners are only exempt from stamp duty when the value of the home is less than $330,000.

In Sydney, a group of homeless people have just been removed from Martin Place. The leader of the "tent city" is Lanz Priestly, pictured. Credit:Daniel Munoz The NSW government scrapped a stamp duty concession scheme for seniors in 2012, despite signs of a deepening of the housing affordability crisis, and has no specific measures in its new housing affordability package to encourage older NSW residents to downsize. According to the Grattan Institute's Brendan Coates, the disincentives have fuelled the level of inequality laid bare in the figures, as more young families are shut out, not just from buying a property, but from paying the rent with fewer houses and rooms on the market. Rough sleepers along Elizabeth Street in Melbourne. Credit:Joe Armao Mother-of-five Joanna Karalis spent up to 50 per cent of her income on rent in Hurstville for a decade while supporting several children with disabilities.

"It was just horrible. I was constantly depressed and getting at the kids, which was even harder because they hadn't done anything wrong," she said. Illustration: Matt Golding "It was so hard with one wage just to keep the electricity, gas and water on and buy school uniforms for the kids." The figures show that in Ms Karalis' former local government area of Georges River there are now 664 four-bedroom homes, 169 five-bedroom homes, and 37 six-bedroom homes with only one person living in them, while one-in-six residents suffer from rental stress.

In Melbourne city, where 35 per cent of people suffer from rental stress, there are 43 six-bedroom homes with one occupant. In Port Phillip, where one in five struggle to balance rent with bills, there are 167 four bedroom homes, 30 five bedroom homes and 29 six bedroom homes with just one person living in them. It's a similar story in the Sydney local government area, where 95 six-bedroom mansions are practically vacant, while up to a third of residents battle rental stress. In Randwick, there are more than 500 four- and five-bedroom homes that have just one person living in them, while up to 20 per cent of residents push their income to the limit for a place they can afford. "You can't wait for the baby boomers to pass away to get those houses on the market," said Mr Coates.

"A lot of people in their 60s can expect to live for another 30 years. Try telling younger Australians that they have to wait for that to happen to be able to afford a house that is close to their job." Mr Coates said restrictive planning laws in the east coast capital cities meant smaller properties that would allow older Australians to downsize aren't being built. "We need to shift the subdivision laws in our middle and inner-ring suburbs to create the kind of housing that everyone needs," he said. "Anything beyond the CBD it's really hard to get beyond medium to high-density housing. In the inner and middle suburbs, they have barely changed in decades: that is part of the reason we see house prices rising and rental stress.

The national peak body representing the interests of older Australians, the Council on the Ageing, said it's clear an older individual sitting on a four to six-bedroom house is an under utilisation. "There are arguments that some of the older constituents are reaping the fruits of the 'not in my backyard' attitude to medium density development for example," said COTA chief Ian Yates. "The dilemma in 'right-sizing' is if they want to move to an appropriate home, then it's not only going to cost you money through stamp duty, but they want to stay in an area that has the right services." Mr Yates said some of the measures announced by Treasurer Scott Morrison in the May budget such as allowing seniors to contribute the proceeds from the sale of their house to super, could still discourage them from selling by counting against them on the aged pension test.

The government has restricted the perk to family homes owned for more than 10 years. "Under the 10-year rule a person who might otherwise decide to move is probably going to be advised by their financial planner to wait another two years," he said. "Public policy could perversely slow down people moving who were otherwise going to do to it." he said. The St Vincent De Paul society says many of those who are living in largely empty homes are older women, too afraid to move out of their communities where they are comfortable with support services.

Cruelly, single women are also the fastest-growing group of people with no home at all: the number of people sleeping rough in the Melbourne CBD doubled over the past year and increased by 10 per cent in Sydney over the past six months. "Worsening housing affordability has pushed people down the line," said Mr Coates. "People who used to be able to afford housing are being displaced. With a shortage of housing stock, something has to give and you end up with people in really rough circumstances." In the Sydney city area alone there are more than 6000 empty rooms in three, four, five and six-bedrooms houses - capable of housing the residents of Martin Place's homeless tent city hundreds of times over. "Wherever you look around the city now there are cranes on the skyline, but they aren't building a national housing plan to solve this problem," said the CEO of St Vincent De Paul's social and affordable housing fund, Brian Murnane.

Ms Karalis, who is now in permanent low-cost housing and running a charity to help others in need, said she had been working with volunteers to help those sleeping rough in the tent city after it was dismantled by NSW police on Friday. "It's frustrating to know that there are so many empty rooms out there that people can sleep in and they are not being used," she said. "It's scary to think that it can be such a cold winter and there is nowhere to sleep."