National is promising that grants for first-home buyers on modest incomes will be doubled - to up to $20,000 for a couple buying a newly built home - if it is re-elected next month. The existing KiwiSaver grants of up to $10,000 a couple will remain for qualifying buyers of existing homes, but the cap on the value of the properties that can be bought has been lifted throughout the country. It will be $550,000 in Auckland.