The thing is... rents rise over time while a fixed rate mortgage balance doesn't.

So I think you'd need an additional 2-3% return on that interest-bearing account just to account for inflation.

In most cities the price to rent ratio makes no sense so I'm a renter for life. I do fantasize about a 2.5% fixed 50-year interest-only mortgage and never paying it down. If only those existed. I think Sweden comes close but the rates there are adjustable.