People who can afford to buy overseas property for cash "just in case" are probably not worried about making an extra $3k/month, not if it adds the headache of being a landlord.

Note that £20-45k/month (US$25-60k/month) is more like the going rate for these properties.

http://www.nestoria.co.uk/mayfair/property/rent/2?price_min=...

But either the owner isn't interested in the money/hassle/attention, or occasionally uses the property — it's difficult to show off your fancy London apartment if people are living in it, and you can't casually lend it to friends or relatives.

I reckon people with $25-60/month to rent out these properties would already have enough money to buy their own homes slightly away from the city center

They probably do, but that doesn't mean they want to live there.

I pay $2k to live in a city centre. I could pay half that to live at the edge of the city, but then I'd be at the edge of the city.

They probably don't want any more of a paper trail leading back to them than they have to.

A net zero property seems like it could generate less paperwork if the management balanced incomming and outgoing payments, (less their fee.)

How exactly do they pay utilities/etc without anyone noticing their transfers? But I don't believe they are successfully hiding anything in any case, governments want everyone to be guilty of something so they can achieve whatever political outcome they need through selective enforcement.

There are people that behave in ways I considered pretty irrationaly with their capital... and they work out.

If they're getting an absurd percentage increase from property values alone, an extra few percent won't make a difference.

Not everyone min-maxes their capital. Governments probably end up eating them through inflation and taxes in the long run (but in the long run, we're all dead).

Being a landlord is a huge hassle, and it makes the property harder to sell when you need the cash back.

Yep, tenants laws add a new layer of complexity to the asset, which as a wealth sink isn't really needed.