Well everything has its risk. Certain stocks could be affected by floods and earthquakes depending on what you are holding. A war for sure would have an impact on pretty much everything else as well.

Maintaining a small 3 room apartment is not that much of a nightmare. We aren't talking about a villa with a pool, a garden, vegetation, a couple bathrooms.. just small city apartments which will always have a demand. You can get them in places known to never be affected by earthquakes or floods, just study the area before buying. Fire or gas explosion is always there tho, but that's life.

Perhaps you could look at parking spots. You can rent them too and they have next 0 maintenance since it's just a small rectangle of cement. The % of danger of flood is much higher too, since they are underground. But even then... assuming your car isn't there, the person renting it will have the problem, not you. If it floods, it will dry, again it's just concrete, nothing of value on your name is lost. Parking spots seem like a winner in terms of passive income. Im not sure how taxes go in these, but there should be a good demand for parking spots in cities.

I know a family that owns an entire parking building next to an airport and they make millions out of it. They've had it for years and family keeps inheriting it. A money making machine.

Having an entire building is maybe overkill for most of us, but with 20 to 50 spots you could be very well off. When BTC goes to $500,000 or so you will be able to afford a bunch of these with a single BTC.