The billion-dollar couple is making monthly payments of nearly $150,000.Mark J. Terrill/AP Images Beyoncé and Jay-Z purchased a Bel Air estate for $88 million. They put 40% down and financed the rest with a $52.8 million mortgage from Goldman Sachs. With historically low mortgage rates, taking out a loan allows them to put their cash to better use. Beyoncé and Jay-Z, the billion-dollar power couple, have finally put down roots in Los Angeles. The entertainment moguls bought a 2-acre hillside estate in Bel Air earlier this year for $88 million, making it the sixth-priciest home purchase in the history of Los Angeles. In addition to 30,000 square feet of living space housed in six glass-walled structures, the ultramodern property has four outdoor pools, a spa and wellness center, a full-sized basketball court, and a 15-car garage. Despite holding Forbes' title of the highest-paid celebrity couple in the world, with a combined fortune of $1.16 billion, Beyoncé and Jay-Z took out an eye-popping $52.8 million mortgage from Goldman Sachs for the purchase, The Los Angeles Times first reported. That leaves the couple with a huge monthly payment of $149,600, according to the loan document, which is public record. The national median home value, for comparison, is $200,700. Keeping their mounds of cash liquid could be a smart business decision. For starters, it helps to maintain their lavish lifestyle. But it could also allow them to continue investing heavily in tech companies, presumably earning returns greater than the amount of interest they'll pay, considering mortgage rates are still historically low in the US. "Depending on how their portfolio looks — what they've invested in — I think there could be a huge benefit [to Beyoncé and Jay-Z]. It gives them flexibility, and they could pay the mortgage off anytime," Robert Cohan, a managing director at Carlyle Financial in Los Angeles, told Business Insider. Based on mortgage applications for new home purchases in July from the Mortgage Bankers Association, the average American applied for a loan of $329,483. At 4% interest over 30 years, that's a monthly payment of $1,573. Beyoncé and Jay-Z will be paying about 95