how do we proceed with the sale with Power of Attorney document?

Laws vary from State to State. The best thing to do, in my opinion, is visit your local Motor Vehicle Agency and ask them. I believe a person has to be incompetent before you can act on their behalf with the Power of Attorney. But I'm not a lawyer. Hope that helps! Jim

Your elderly mother can't drive anymore, but can she sign a signature? That's all that's needed. Or if not, you just forge her signature; this is done frequently. This is just a car sale, it's not like it's a Pentagon contract. Talk to the buyer outside and tell him you have to go into the house for your disabled mother to sign... Out of the buyer's sight.