In Finland we apparently used to have mortgages that were just Euribor + bank margin, meaning that if the Euribor rate went enough into the negative, the bank would be paying you interest.

These days mortgages are capped though. My mortgage rate is MAX(Euribor 12m, 0%) + 0.5%. Unsurprisingly I have never paid more than 0.5% interest.

I was looking at mortgage for a house, paying 30% upfront, so I would only need to borrow 500k USD.

At fixed rate 30yr, it was 1% + some fees.. so total cost of the loan over 30 years would be 35k USD.

The flex interest rate (adjusted every 5 years) was a current rate -0.25 + fees. In total that would cost around 10k USD over 30 years. (Of course with flexible interest rates, the rates could go up).

So I think most of the cost is now just fees... Looking at owning vs. renting it's quite competitive.

Last time I looked, the interest is negative if you get a mortgage that floats. However, they’ll add some fees that are also a percentage of the remaining loan, so that you are in effect are still paying interest.

So no, it is not capped, but the interest has to become even lower before the interest on your Mortgage helps pay itself off.

Some actually do