Canada

The first link was to give the total numbers of units and the separation between single and multi owners, the second link refined the multi owners into double or 3+

So multiple property owners are already not a big group, then not even half of them have a rental in the same city they live in. This isn't surprising, nor a huge problem given what I said early that only 3.5% of BC properties are third or more properties.

Like I said at the start, go ahead and tax the shit out of this if you want, but do not expect such a tax to in any way change the overall market it simply isn't a big enough problem to impact prices in any useful way because it doesn't address the core issue which is that ALL home owners are profiting off land appreciation, even (and primarily) those who only own one property.

I say this as a homeowner, my home has appreciated by as much as if my wife and I had an entire third income over the last 15 years. It's money that I didn't do anything to earn, and it's money that will need to be earned by someone younger in order to buy my property when we sell it and downsize as we age.