Mark Zuckerberg's $7m house

Zuckerberg's wife Priscilla, and their dog Beast in the kitchen.

Beast caught looking for a snack in the fridge

Another view of the exterior of the house.

The two-floor white wood-sided home is ensconced behind a gated drive and a wall of groomed shrubbery, about three miles (4.8 kilometers) from Stanford University and three miles from Facebook’s Menlo Park headquarters.

A view of the outdoor pool.

Perhaps more astonishing than Mark Zuckerberg refinancing a 1.05% home mortgage rate is the fact that the 40th richest man in the world needed a mortgage at all. After all, why would someone worth over $15 billion need to borrow money to pay off a $7 million home? Well, if you can borrow money at 1.05%, you're basically borrowing money for free, reports Bloomberg. So Zuckerberg would be dumb not to.

A guestroom in the house.

One of the dining rooms.

The five-bedroom, 5-1/2-bath house was built in 1903 on a 9,011 square-foot (837 square-meter) lot.

Zuckerberg's mansion includes an outdoor gazebo with wood-burning fireplace, salt-water swimming pool, spa, and car porch.

Another dining room in the house

The luxurious bathroom.

Another view of the bathroom

Zuckerberg and his wife Priscilla in the kitchen.

Zuckerberg's office in the house.

The benefits of an adjustable-rate mortgage (ARM) are that the interest rates can be lower than a fixed-rate loan -- as evidenced by Zuckerberg's 1.05% rate. However, should the housing market unexpectedly heat up, the cost for borrowing money can increase, causing ARM rates to skyrocket. For most borrowers, this can be a problem, as that 1.05% loan can become a 6% or 7% loan. In fact, ARM rates skyrocketing is a frequently-cited reason for foreclosures during the past several years

However, for borrowers who have lots of money, the adjusting interest rate of an ARM poses little risk as the borrower can simply pay off the loan when the interest rate is no longer favorable. For example, if interest rates creep up, Zuckerberg could simply pay off the loan with his cash on hand. While Mark Zuckerberg's mortgage rate may be an example of the rich getting richer, the fact is that Zuckerberg is a near-zero risk to banks. His lenders are assured a return regardless of what the market does. The same can't be said for most every other borrower.