I agree with all of the responses, below. This is a question better asked of an attorney.
NOTE: If you fail to find an attorney that will readily address this question over the phone (requesting that you come in for a consutation and charging you for same), I'd contact the National Bar Association for an attorney referral. Attorneys who have open themselves up for recommendation by the Bar have typically also agreed to only charge $50 or so for the first 30 minutes of consultation.
rancesca Patrizio, Realtor Associate
NJAR Circle of Excellence '06-'07
REALMART REALTY - An AFFORDABLE Way to Sell your home
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The person may sign a Quit Claim Deed but, it may not release your partners name from the mortgage and it may still cause you problems with the partners creditors who may place a judgement on the property long after you have paid the partner off and he has signed the Quit Claim Deed. See an attorney.
Although this would be best answered by an attorney, As i am not an attorney and this is not legal advice but, my opinion.
As I know it , when a person buys out another party, an actual closing takes place and it would be just the remaining persons interest.