Income-testing has been used for other Government housing initiatives - including the HomeStart grant for first home buyers - to ensure that demand is limited to only those who need them most.
The HomeStart grants are limited to sole buyers earning less than $85,000 or two or more buyers earning less than $130,000.
In the case of KiwiBuild, the Government feels affordable housing should not be restricted only to those on low or modest incomes.
For people on the lowest incomes, the Government has committed to expanding social housing. The Budget included $4 billion in funding or borrowing to build 1600 new state houses a year.
Further policies are being devised for those who are struggling to get into affordable housing, including a possible shared equity scheme.
Twyford said last week that officials were looking at a scheme which would allow a third party such as a bank or a government agency to co-own a property by taking on a share of the mortgage.
That would reduce the owner's deposit and weekly mortgage payments.
The owner could then buy the remaining share off the third party when they could afford to.
There are likely to be other KiwiBuild requirements such as a minimum length of stay before resale.