Short answer: Varies by region. Auckland highest (~$875,000 for new builds). Check Kainga Ora website for current caps.
The government sets maximum house prices for each region. If the house costs more than the cap, you cannot get the First Home Grant or Loan. Auckland has the highest cap. Smaller towns have lower caps. Check the current caps before you start looking.
Region: Auckland
House Price: $900,000
Price Cap: $875,000
Over By: $25,000
Result: Not eligible for First Home Grant