It depends on the stage of the real estate cycle.
During the beginning, middle, or expanding stages, it is better to have mortgages, so you can leverage more properties to maximize the profit.
The more closer to the peak, it is better to pay off the properties, so you have a better position to ride out the next recession.
The real estate market is still very strong, should have at least a few months years expanding before reaching the peak. I’m still purchasing more properties using leverage today.