Housing Minister Phil Twyford spoke on the KiwiBuild program at the BuildNZ conference in Auckland

Couples earning up to $180,000 a year will be allowed to buy affordable KiwiBuild homes - as long as they live in them for at least three years.

The Government is unveiling on Wednesday who will be eligible to buy one of the 100,000 affordable KiwiBuild homes it is hoping to build over the next 10 years.

Documents released to Stuff show the criteria will include an income test - but one that will still allow 92 per cent of first home buyers to get into the scheme.

LAWRENCE SMITH/STUFF Conservative analysis from MBIE says two thirds of first home buyers could not comfortably afford the first KiwiBuild homes.

The income cap is $120,000 for a sole buyer or $180,000 for a couple.

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The documentation spells out the main points of the criteria.

Both citizens and New Zealand permanent residents will be eligible.

The homes will be available to all first-home buyers and most "second-chancers" - usually people who go through a divorce and have lost property. Second-chancers must not have assets exceeding $120,000 in Auckland, $100,000 in most other cities, or $80,000 for the rest of New Zealand.

First-home buyers will not be subject to a financial asset test - they will simply need to be buying a first home.

The relatively high income cap will allow 92 per cent of first home buyers to be eligible, documentation from Housing Minister Phil Twyford's office shows.

Those who purchase a home will need to live in it for at least three years without selling it, but will be able to rent out spare rooms to flatmates.

Some purchasers will be able to sell the home within three years if special circumstances such as a death or serious illness occur - but they will need to apply for permission from the Government, who will consider each person on a case-by-case basis.

For the first years of the scheme, the homes will be balloted, meaning every eligible buyer who enters will have an equal chance of buying a home.

Potential buyers can register their interest online but will have to go through an eligibility check before being entered into the ballot.

The income bracket is substantially higher than the one for the HomeStart grant, which cuts off at $130,000 for couples and $80,000 for single buyers.

Twyford said there were plenty of people earning close to the limit struggling to buy homes in high-cost areas.

"We know that New Zealanders at and below these incomes are struggling to buy a home, especially in high demand areas such as Auckland and Queenstown," Twyford said.

"For instance a couple of teachers may have a combined income of between $150,000 and $170,000. For a nurse and police officer earning upwards of $120,000, and for an engineer living alone, $90,000. A decade ago these families would have been able to afford a home, but they are now locked out of the market."

Twyford had earlier indicated he would not be keen to introduce income caps for the scheme.

Documentation released by Twyford's office shows that households in the $80,000-$180,000 range have experienced the largest decline in homeownership over the past decade - and that nearly half of all families with children fall into that category.

KiwiBuild homes have price caps that differ across the country.

Three-bedroom homes in Auckland and Queenstown will cost $650,000 or less, with two-bedroom homes costing $600,000 or less and one-bedroom homes costing $500,000 or less.

All KiwiBuild homes outside of Auckland or Queenstown will cost $500,000 or less.

ROSA WOODS/STUFF The Government has scrapped its plans for a Kiwibuild Visa in favour of wider changes to immigration settings.

The Government is planning a gradual ramp-up of KiwiBuild homes, with 1000 built by July 2019, 5000 the following year, and then 10,000 the year after that.

Half of all the homes will be in Auckland while the other half will be spread out across the rest of New Zealand.

National has repeatedly criticised the policy, saying it will suck up capacity from the private sector while costing the taxpayer money.

Housing spokeswoman Judith Collins has also said eligibility criteria should lock out Kiwis coming home from long periods working overseas and not paying local taxes - something the criteria announced on Wednesday will not do.

National's finance spokeswoman Amy Adams said the income cap was an admission of defeat by the Government, as it showed poorer people were not going to be able to afford KiwiBuild homes.

"Twyford has set the eligibility criteria for KiwiBuild so wide that 92 per cent of first home buyers are eligible. That's because he knows he will fail to deliver houses that are affordable to lower and middle income earners," Adams said.

"Having such a wide criteria and a ballot system to determine the lucky few to get a subsidy is unfair and will mean struggling families could miss out in favour of higher income families and people with significant cash assets."

"There are 24,000 first home buyers a year and the Government is now only planning to deliver 1,000 homes in its first 20 months in office - so they should be targeted to lower and middle income families."

KiwiBuild has a $2b budget, which the Government wants to "recycle" as the houses are sold at-cost price to buyers.

Home ownership has been falling for the past three decades, from 75 per cent in 1991 to around 63 per cent in recent years.