If the man is 'legal incompetent', he can not give a power of attorney now, it is too late. You'll have to file for legal guardian or conservator over him in probate court in the county where he is located. It is not an easy process for a non lawyer, but you can seek help from the local legal aid society, local law schools, local bar association pro bono panels, etc. Ask for help and referrals locally. Try asking attorneys listed as probate specialists fir referrals if pro bono or reduced fee. Worst case scenario is to get the Public Guardian involved, as they will take over and you and the man will lose control.
