Power of Attorney

I have a question of Power of Attorney. What so it mean?

We need to sell the house and my hu*****and works in another city. So we need a power of attorney to sign the contract for him. I wonder if I can be his power of attorney. How to do it? go to the bank to get authorized? or hire a attorney?

Does anyone know how much to hire a power of attorney in MD? please recommend a one if you have experince. Thanks