Ask HN: How do the ultra rich maintain homes when they are not occupying them?

Surprizingly, most don’t. You need to run the water, maintain a standard temperature in the house throughout the year, flush regularly, use all the appliances, etc. You can’t just have your gardner coming once a week, your cleaning lady twice a month, you need someone to live in your house to make sure it works properly. It’s like an engine in a car or a motorcycle, it needs to run to stay healthy, otherwise it needs to be conditioned for storage purposes.

So, to answer your question, family members, friends, etc are what ultra rich people use in order to maintain their real estate portfolio. Not only personnel. Personnel is useful for an occupied house only.

Not sure about Europeans or Americans, but here in Latin America they have butlers, "ama de llaves" (best translation I can find is housekeeper) or groundskeepers living 24/7 at the property (not in the house proper, usually on a separate house).

The same way they maintain them when they are occupying them: they have staffs of workers to clean, maintain the grounds, provide security, etc.

The book Empty Mansions has an extreme account of this.