A conventional mortgage typically requires a down payment of at least 5% of the purchase price. For a $400,000 house, a 5% down payment would be $20,000.
However, a larger down payment can help you qualify for a lower interest rate and reduce your monthly mortgage payments.
For example, a 20% down payment on a $400,000 house would be $80,000, and this would allow you to avoid paying for mortgage default insurance, which is required for down payments less than 20%.