I'm 62, my wife is 73. We now have TWO mortgages, one on our new home and one on our old, not-yet-sold one.
We priced in the mortgage on the old home into our FIRE plans for the next 12 years after we retired. We had lots of safety margins built into our plan so we didn't have any worry about the mortgage on the old house.
I just went on social security in January. The new SS income is about $2500 less than the new mortgage and I was paying about half that extra on the old mortgage. So, realistically, it will cost us an extra $4,000 a year if we include utilities, and less that the first year.
And, of course, once the old house sells, we'll be able to put a goodly amount onto the new mortgage or buy stock, whichever seems the best choice at the time, and we'll be almost $20,000 in stable income ahead of where we were at the end of last year.
We only owe about $141k on the old house and it should have sold for between $260k and $300k. So, even if we sold it for cost just to ditch the utilities and mortgage, we would still be better off this year than last in terms of income.
Or we could rent it for enough to cover the non-equity portion of the mortgage and a bit, so that it lowered our cost basis while the market was low and preserved our equity in the house until times were better.
So, for us, it makes sense even in these troubled times.