I am a Florida attorney-the answer in Florida would be NO-not unless he obligated himself by signing a contract.
Social Security payments are exempt form creditors in most states.
Hope you get NM attorney's answer.
The answer given does not imply that an attorney-client relationship has been established and your best course of action is to have legal representation in this matter.
New Mexico is a community property state, which means this could be community debt. You should make arrangements to consult with a probate lawyer in the Carlsbad, Artesia, Roswell area. NM also has certain exemptions that may be relevant, but an attorney would have to review the details of your case, which will require a consultation that cannot be done through this forum.