I agree with SD..."as is" and "no refund" of deposit are big warnign signs. I also worry about what nice new paint jobs on engines are covering up. It is just too cheap to not have problems.
As to living on a mooring in Charleston harbor...I thought they were taking out the moorings and I also thought that live aboards were not permitted there. That is a wicked place to try to live on a boat anyway given the currents, chop and traffic. Do you KNOW that you will be allowed to do what you are proposing if you DO get a boat?
Great town...good luck!