They don't have to ever sell the properties. Property can be assessed by a third party and then function as collateral against a low-interest loan, which is real money.

Not that I think McDonald's will ever really find themselves in a pinch, but if they did, they would additionally be able to liquidate selected properties for cash. When you are rich enough, the promise of having money in the future is just as good as actually having money. It doesn't work like that for most of us, but that's the nature of risk assessment in finance.