> I’m not sure how charging taxes on landlords is spending public funds that they would have otherwise had if that tax was not present. There’s no loss of public funds here.

It's not, but giving tax breaks to home owners is. Giving tax cuts to home owners and not home renters is by definition not equitable, you'd be favouring one group of people over the other. And if you look at who has it economically better, you'd statistically favour to give tax cuts to the economically better-off group most of the time in almost all countries. If you then, on top of that, tax landlords, it leads to even higher rents and even larger disadvantages for the renter class. That's something you haven't acknowledged, except by saying 'perhaps some of these renters can become owners, too!' -- and that's a fair point, but also wholly insufficient. We know not everyone can, needs or wants to be an owner. We know a rental market is important. Yet the tax manipulation you suggest very much disadvantages the usually poorer-than-average income rental group and favours the richer-than-average owner group.

> I’m also not sure how government policies that deprive people of the ability to own their own home (since they are priced out of the market by landlords, and landlords now own way too much of the housing stock) is a good thing.

What policies are you talking about that would deprive people of the ability to own a home?

> Right now in NZ about 1/3 of people rent [1]. It’s an all time high across all age groups.

Just like in the US. Just like in my country in Western-Europe. I'm not sure how large you think it should be, more, less? Should we strive towards anything at all?

> but seems reasonable for people given the choice to own their property vs pay someone else, that they would want to own the property.

That doesn't seem reasonable at all. Would you say the same for example, in a world with a shrinking population, large amounts of vacant land and cheap technology to mass-construct homes? In such a world, property prices would (ceteris paribus) drop over-time. Most people would be entirely disinterested in owning a home in such a world. Why not simply cheaply rent, wherever you decide to live, move as often as you want, as often as your tastes or moods change. Of course this world is hypothetical, but I use it to show that the choice to own a home isn't natural, it's conditional.

Now I agree that in the current market, it's preferred to own a home, because prices and rents are going up, but a mortgage can be more or less locked in. Of course people prefer a 30y mortgage contract at 2k per month and see their home equity triple in 30y, than to rent at 2k and see their rents triple in 30 years, for example. But the point is that this ownership preference is thereby conditional on what the market does. At the same time, every academic study, every central bank etc in the world is saying that low interest rates and tax breaks are pushing prices up. That means you're doing two things. The very condition you have that says 'owning is preferred' is in fact exacerbated by your policy to subsidise owning (with public funds), which screws over the rental market and everyone unable to own (which has always been 20-30% of the population, typically the poorest one). And second, you're favouring this generation over a future generation. That subsidy isn't sustainable, but creates massive wealth for current owners (who bought into a market at $200k homes) at the expense of future owners who are born into a market where a home costs $1 million. That also is poor public policy.

> Also does 1/6th of all residential property NZ need to be owned by someone with 20+ properties under their belt? [2] Is it good use of public funds to allow such behaviour rather than say encouraging (non residential rental) businesses to grow and expand

I don't really see the big issue with minor property concentration. They all must rent out at market rates. Someone with 20 properties (in a country with a few million properties) is not setting the price levels, but just following them, just like anyone with 1 property would. Would it help if the company or person who owned 20 properties, would instead be 5 companies or persons who owned and rented out 4 properties?

> Is it good use of public funds to allow such behaviour rather than say encouraging (non residential rental) businesses to grow and expand

I don't see what spending of public funds you're referring to, thereby also not sure how that prevents businesses to grow and expand.