Well, if you are worth billions and only spending millions, then you can borrow for a very, very long time before the interest payments get hard to pay. If you

Well, if you are worth billions and only spending millions, then you can borrow for a very, very long time before the interest payments get hard to pay. If you do end up in that position, you can always borrow more to pay the interest(the US govt does this). It's nothing magic here, you even get to deduct the interest you end up paying on your taxes usually. The rates probably not that much lower, the lenders still have to make money and they really don't like to get stuck holding the bag. They have risk departments who (hopefully) carefully analyze how much borrowing they are doing and making sure they are the ones holding all the cards if it ever comes crashing down.