Your mortgage may come with a bonus: credit-card reward points. Chase recently announced it will give 100,000 reward points, worth up to $1,500, to existing credit-card customers who take out a home loan with the bank between now and Aug. 6. The bank is not the first to offer credit-card perks in exchange for home loans. In the last year, Capital One offered cardholders earned air travel miles if they purchased property or refinanced their home with the bank, Wells Fargo gave out rebates to cardholders to use for its mortgages and home equity loans, and Quicken Loans doled out points for some of its borrowers.

However, the sheer size of the mortgage offer from Chase is new. "The 100,000 points is one of the most generous — and perhaps tops — that we've seen for financial products," said Greg McBride, chief financial analyst at Bankrate.com. "But it doesn't negate the need to shop around for the best deal or justify settling for an inferior loan that could cost far more in the long run." Banks are spending more on credit-card rewards to build loyal customers for other parts of their businesses, said Nick Clements, co-founder of MagnifyMoney.com, a price-comparison website. Millennials are a prime target. For example, at Chase, 36 percent of mortgages last year were taken out by borrowers who were under 35 years old or younger, up from 20 percent in 2015. A recent MagnifyMoney analysis found that the six largest credit-card issuers spent $22.6 billion on rewards, more than double the $10.6 billion they paid in 2010. (See chart below.)