How many spare houses, spare cars, spare anything do you keep. These aren't a couple of dinner plates. These are machines that are hugely expensive. Just having

How many spare houses, spare cars, spare anything do you keep. These aren't a couple of dinner plates. These are machines that are hugely expensive. Just having them costs money. Where do you park it? And if you need one how do you get to it. Major airlines do keep spares, but only at their major airports.