After falling into debt 30 years ago, Lee Blake, 81, was forced to sell her home and has been living on and off the streets ever since.

Unable to afford the rising cost of rent, she has spent the last few years living out of a bus on the northern beaches of Sydney.

"I couldn't pay $300 a week rent when my pension's $280 and I do like to eat, so if you live in the street you think, 'Well, at least I'm eating,'" she said.

"You're never really comfortable, you're never really happy, you're never really safe, but that's life.

This is the bus Lee Blake lived in. ( ABC Nerws )

"I grew up in very big family, but gradually they all disappeared, they're either all dead or they've vanished, I don't really have contact with anybody."

A new report from Mission Australia shows that about 22,000 people aged over 55 sought homelessness services between 2015 and 2016, up 15 per cent from the previous year.

Mission Australia chief executive Catherine Yeomans believes unless action is taken to address this issue, the number will continue to increase.

"We need more social and affordable housing, we need more support accommodation for people who are suffering health issues," she said.

"From 2030 to 2050 we expect the number of people over the age of 65 to double, so if we're already seeing high rates this problem is only going to get worse unless we invest in the future."

She now has a home

Ms Blake secured a social housing unit eight months ago with the help of her Mission Australia case worker, Lisa Belleri.

"We'd had a lot of rain for a week or so and Lee rang me up one day and she was really distressed," Ms Belleri said.

"She said that the bus was leaking, she was sleeping on a wet mattress and so I called Housing and advocated even further and she had an offer not long after."

While Mission Australia's assistance has proven to be invaluable for Ms Blake, she said that staying optimistic got her through the hardest years.

"I haven't had a choice, I've had no choice. I haven't wanted to. Every now and again I'm happy but I do a Pollyanna," she said.

"That's what gets you through, that's what got me through all those years, and that's what gets me through today."

'Older women are particularly vulnerable'

Catherine Yeomans is concerned about the growing number of older homeless people. ( ABC News )

Ms Yeomans said there are several factors that contribute to vulnerability in older populations, especially for women.

"Some people are finding financial difficulties, so later in life they might not have any retirement savings, they might be in and out of work, and unfortunately family and domestic violence is another contributor," she said.

"Older women are particularly vulnerable because they've had caring responsibilities throughout their working life, they may have secured part-time work or intermittent casual work, and they may also find it hard to secure ongoing work when they reach their 50s and 60s before they qualify for the aged pension."

As well as helping people like Ms Blake live independently, Mission Australia also runs aged care facilities for older homeless people such as the Annie Green Court in Redfern.

"Seventy-two residents call this place home," Ms Yeomans said.

"It's supported accommodation targeted to people who otherwise would be spending decades in their later life on the streets or in other homeless accommodation.

"People who are older, over the age of 55 or over the age of 65, we need to make sure that they can age gracefully with dignity and respect."