below 20% you usually need mortgage insurance (PMI) in the US. PMI is usually not too expensive with 10% down - for example when I bought a house with 10% down

below 20% you usually need mortgage insurance (PMI) in the US. PMI is usually not too expensive with 10% down - for example when I bought a house with 10% down, the PMI was 1% of the loan value up front. When you consider the time it would take a family to double their down payment savings, it can make sense in high cost markets. You can go as low as 5% down, but the mortgage insurance gets a lot more expensive. The general guidance is still 20%, though, because you're less likely to go underwater, and it shows you're committed to the idea, the area, etc.