Landlords have backed Auckland property investor Ron Goodwin who says they should not to be "too kind" because tenants take advantage.
Mr Goodwin, 74, has 37 properties in Auckland and Waikato generating $14,500 a week in rent.
Tenants have taken advantage on rent negotiations, rubbish clearing responsibilities and even childcare, said Mr Goodwin.
"The kinder a landlord is to a tenant, the worse the tenant treats the landlord. Some tenants go to great lengths to become friends with their landlord, then come up with all manner of hard-luck stories and expect their landlord friend to help them out financially by letting them off paying their rent," Mr Goodwin said.
But landlord Kevin Menzies stuck up for his sector and suggested the Herald's report on Mr Goodwin was promoting "anti-landlord hysteria".
Mr Menzie referred to tenants allowing children to urinate on the carpet and not cleaning it up and hiding household rubbish in the ceiling when they left.
"What crusade are you on and why? Most landlords are like me - working people trying to save for their retirement because the Government has abdicated its social responsibility in this sphere. We don't trust the share market and at least by owning property we can have some control over our investment."
Another landlord, who identified herself only as Chrissie, said she was "too honest and too green" when she decided to rent out her house.
"The tenant I had was a woman with two teenage children and she was the tenant from hell. She has six aliases, knows how to rip Winz off and is still ripping them off, blatantly lies and left my house in a disgusting state. There are three of us ex-landlords getting $20 a week out of her which is pathetic because I know she is getting cash under the table. There are too many tenants out there ruining it for everyone else.
"Additionally the Tenancy Tribunal definitely favours the tenant which is so wrong, and Government departments need to access each other's information and the judges presiding over cases need to step up and take their role seriously."
Mr Goodwin explained how his tenants had taken advantage of him.
"My dad was much less experienced than I am. Dad took to heart all his tenants' sob stories and then gave them very low rent to try to help them. One old lady renting alone in a big, old house always went on and on to Dad about how poor she was. Dad gave her exceptionally low rent with no increase for over 10 years. She finally died leaving behind a huge fortune in her estate."
Landlords should also be wary of tenants' hard-luck stories, he added.
"Experienced landlords know this scenario well. If you give a tenant an inch out of the kindness of your heart they take a mile and expect more and more as time goes on. My rental business is just that; a business and not a charity.
"However, I often go soft on rent rises for a sincere tenant who seems to be struggling financially and who is not wasting their money on cigarettes, booze and [marijuana] as so many tenants do.
"Also, I frequently do all manner of small things to help some tenants, particularly solo mothers, such as taking their accumulated junk off to the tip at no cost to them. After I had once helped a tenant in this manner, she invited all her friends to dump their rubbish and junk on my property in the belief I would take that away for free as well. I didn't.
"A few solo mothers have really abused my kindness. For example, one asked me to mind her 3-year-old while she went up to the shop for half an hour. Four hours later, she finally came back and relieved me of the responsibility with no thanks and no apology!
"As a general rule, the kinder a landlord is to a tenant, the worse the tenant treats the landlord. This is common knowledge among experienced landlords. However, there are some exceptions."
The Rev Mark Beale, who runs a church housing trust which has accommodated up to 20 families, said Mr Goodwin had more than enough earthly riches, so could be far more charitable.
"He's a multimillionaire who can afford to help people. He can afford for them to take advantage of him. People are not treating houses as homes any more but as money-making ventures," Mr Beale said.
The vicar had some more direct advice for Mr Goodwin: "You won't find happiness in money. Jesus said 'shake the dust off your feet'. If you have a situation that goes wrong, you shake the dust off your feet and trust the next tenant."
Mr Goodwin has $4.8 million debt on his properties which have 2014 rating valuations of $13.6 million, but which he estimates are "likely over $18 million".
"I started out with nothing 29 years ago and have built up this rental portfolio through wise buying, numerous infill developments and sheer hard work," he said.
Mr Goodwin will be at the $799-a-ticket NZ Property Investors Federation annual conference in Auckland where hundreds of landlords will impart their own words of wisdom. It's at the Crowne Plaza hotel from Friday to Sunday.
Andrew King, New Zealand Property Investors Federation executive officer, said professional property managers played an important role in the sector and some landlords would be well advised to employ them.
"Not everyone is suited to being a landlord, although most people can manage properties themselves. Professional property managers have their place," he said.
However many landlords had good relationships with their tenants.
"It's certainly cheaper and keeps the cost down [without a manager] which keeps the rent down. A lot of people who are managing properties themselves perhaps should not be and if you are finding you get the wrong tenants a lot and if you don't have the character for it - say you're too nice - you should not be doing it," Mr King said.