I bought a piece of real estate from my mother, and we did a quit claim deed; I have decided to sell the real estate and have a buyer... but the buyers lawyer said that there is a lien on the property where my mother had borrowed against the land many years back, do I have to pay the lien before I can sell the real estate? Am I liable for her dept against the property? I was not aware of the lien against the real estate when I purchased it.

Why wasn't this lien satisfied from the proceeds of the sale when the property was sold to you by your mother? Either way, if the lien is still there then it'll have to be satisfied before the property can be sold. You can use the proceeds when you sell the property to have the lien satisfied.