Watch the video above for the full story and interviews from The Nation.
There are growing calls for a tighter controls around boarding houses.
The housing shortage means they're being relied on for accommodation more heavily by more people, but landlords are not required to register their boarding houses - despite taxpayer money going into them.
Experts say it's allowing rogue landlords to exploit vulnerable people, with some living in brutal deprivation.
Labour MP for Manukau East Jenny Salesa found a house in which a room cost $230 a week. It's infested with flies and cockroaches, and smells of excrement thanks to a lack of doors, windows or a working toilet.
"The closest toilet is about three or four streets away," she told The Nation.
"This landlord still gets a lot of money from these very vulnerable people that have no other place to live. One of the folks that came asking for my assistance said that she used to live on the streets and this is at least a step up from living in the streets, but this is Aotearoa New Zealand - no one should be living in a house like this."
She lodged a formal complaint with Auckland Council, but even after the council posted an insanitary notice on it in March, the landlord - Gurmej Kaur Singh - still charged rent.
The number of people living in the house fluctuates - sometimes it can be up to 10 people. Some are out of jail, some have mental health and addiction issues, while others couldn't find anywhere else to go.
Several told us Ms Singh would often take their cashflow cards to withdraw rent money.
It was a similar story when The Nation visited another one of his south Auckland properties - 65 Great South Road in Papatoetoe. With no running water and no toilet, it too had been deemed insanitary by the council but also had people still living in it - still paying Ms Singh rent.
Ms Singh owns at least five properties, and the rent from some of her tenants who are beneficiaries is paid directly into her bank account by Work and Income.
The Nation asked the Ministry of Social Development how much taxpayer money has been paid to Ms Singh, but it is yet to release that information.
Since 2005, the council says it has received 22 separate complaints about her property at 43 Church St related to filthy conditions , rubbish and caravans on site. But the council says the issues were always fixed at the time.
"It's third world, right in the middle of our city," says Renee Joseph, the Society of St Vincent de Paul in Otahuhu.
"I'm amazed at the state of some of the boarding houses and the rentals around… I can't understand why you've got people who are allowed to live in these conditions and it's ignored and nothing has been done."
Boarding houses are one area of housing that Ms Joseph says operate in no-man's land.
Clare Aspinall wrote her master's thesis on boarding houses. She says nothing has changed in years.
"It's a complaint based system - people don't complain... The issue is enforcement - the regulations are there, there could be improvements to those regulations, but the ones currently in existence aren't enforced."
Te Puea Marae opened its doors last year to people needing temporary accomodation. That offer ended in September, but chair Hurimoana Dennis says people keep coming.
"The sad thing is our leaders have known about this problem since 2010. Quite explicit papers have gone up to Cabinet. It was very clear - be careful, this is what's coming."
Major Campbell Roberts of the Salvation Army says it's more common than many people think.
"There are many situations that people are in that really, you're horrified by what the situation is - but the inability to do something about it is what's really hurting at the moment."
Enforcement isn't often carried out because of the consequences.
"If you've got 30, 40, 50 people in a boarding house and you close it, where do you put them?" he asks. "We've let this thing develop into a crisis situation."
The Nation / Newshub.
