I get the point you are trying to make but mortgages are not a good example of an asset that appreciates. The underlying real estate my appreciate in value, but

I get the point you are trying to make but mortgages are not a good example of an asset that appreciates. The underlying real estate my appreciate in value, but the mortgage itself does not. Investing in mortgages would be an example of a fixed income security. You can of course invest in derivatives like credit default swaps which may appreciate in value, but at that point you are not buying mortgages, you are basically buying insurance (which can appreciate in value if the thing you are insuring against becomes more likely to happen).