Does the Mortgage Have to Be Paid Off Before Selling?

No. You do not need to pay off the mortgage before you sell. The existing loan is paid off from the sale proceeds at closing, exactly as in a normal home sale. Escrow requests a payoff figure from the lender, the loan is satisfied from the buyer's funds, and the estate keeps the remaining equity.

What matters is keeping the loan from going into default while the estate is being administered, since a foreclosure would threaten the equity. As long as payments are maintained or the home sells within the lender's timeline, the payoff at closing is routine. This applies to regular mortgages, home equity lines, and reverse mortgages alike.