Homebuyers are flocking to a type of loan that offers a lower mortgage rate. But they often require bigger down payments, and lenders don't like to give them.

Feverpitched/Getty, Tyler Le/BI

• Homebuyers seeking lower mortgage rates are snapping up a rare type of loan.
• Assumable mortgages allow buyers to take over a seller's original mortgage.
• But only government-backed loans are eligible, and they require higher, all-cash down payments.

A type of mortgage that can offer ultra-low rates is becoming more popular among homebuyers — but they're rare and difficult to come across...