We ask, what income do you need to buy a house affordably? The range is surprisingly wide depending on where you choose to live, even for Aucklanders

Discussion of housing affordability is usually about high house prices and low interest rates which help to keen mortgage payments down.

Our housing affordability stories test how incomes (take-home pay) relate to mortgage payment obligations.

We say, if you have to spend 40% or more, then the mortgage is not affordable.

We do this for first-quartile houses as a proxy for where first home buyers might enter the market. Our assumption is that you do this when you are in the 25-29 age group, and have partnered up. "Household income" is our fundamental income unit, and we report results based on median household incomes for each age range.

We then look at the next step, and do that in two ways; either trading up to a median priced home when you are in the 30-34 year age band, or doing it in the 35-39 year old age band.

Each of this two scenarios give a different level of equity from the first home purchase to take in as a deposit for that next change. In the past there have been capital gains that bolster the equity available.

But there is another, more direct way of looking at what you require: what gross income do you need to buy a home using all the normal assumptions.

If you live in Auckland and are buying a first quartile home, you will need a gross household income of $110,169 per year (assuming you can raise a 20% deposit of $132,000).

But you don't have to live in Auckland. If you live in Hamilton, the household income on the same basis to commit to an affordable mortgage is $68,795 while in Tauranga it is $85,706. In Wellington City it is $86,737, in Christchurch it is $54,620 and in Dunedin it is only $44,483.

Living is some regional centers lightens the load even further; in Whangarei you will need an annual gross income of $50,136, in Napier $56,416, in Palmerston North $47,072, New Plymouth $52,288, Nelson $62,695 and Invercargill just $26,976.

And Aucklanders who don't need to live near the centre, the incomes required are smaller too, although still high by comparison with the rest of the country; in Papakura you will need $89,361 while in Franklin it is $87,675 required.

But the fiercest requirements are in the heart of the Auckland urban area; an annual household income of $130,790 would be required to live in Rodney, $141,100 on the North Shore, $108,295 in the Waitakere region and a similar amount in the Manukau area. And remember, these are incomes needed for first quartile homes. (The central Auckland isthmus data is not a good indicator as it is a mix of some of the most expensive leafy suburbs in the country, a wide range of townhouses and apartments, and inner-city shoe-box apartments. We just don't have the data for each of these disparate groups.)

But the take-away from all this is that the range is enormous. Whanganui is the most affordable centre for first home buyers requiring an annual gross household income of just $21,343 to get an affordable mortgage, right the way up to Auckland's North Shore's $141,100 requirement.

Here is another way to view the different levels of income you would need for an affordable mortgage assuming you want to buy a median-priced house and you had a 20% deposit:

We are still learning how to embed and control this feature, so bear with us. If it locks up on you, just refresh the page and try again. Selecting a city in this map should reveal the income you would need to buy a median priced house affordably in a hover box.