A power of attorney is a relatively simple document that an attorney should be able to prepare for you quickly. I do not recommend using forms that you find on the internet or in office supply stores as they may not meet the needs of your particular situation. My office is located in Hampstead, NH and is available to assist you. 603-329-5200.
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I would take Ms. Sapeinza's advice....if your father has the capacity (mentally) to do so, he should execute a power of attorney (and also do his other estate planning). His inability to physically sign is not an obstacle to doing this as 1.)someone can sign for him at his direction, 2.) he can sign with a simple mark or x in most situations...but defer to the NH attorney for specific advice.
This is not legal advice nor intended to create an attorney-client relationship. The information provided here is informational in nature only. This attorney may not be licensed in the jurisdiction which you have a question about so the answer could be only general in nature.
Visit Steve Zelinger's website: http://www.stevenzelinger.com/
If your father has the requesite capacity he can sign a power of attorney. It doesn't have to be a pretty signature, n "X" will do if properly explained. As Attorney Sapienza suggests, do use a form you get online or at a office supply sore. Spend some a little money and have it done right by an experienced elder law attorney. Make sure the POA has an unrestricted gifting power.