A power-of-attorney is a written document where you, the Principal, appoint an Agent to make financial or medical decisions for you when you can no longer do so for yourself.  This is a crucial document in your estate plan that is relatively inexpensive.  Otherwise, a Guardian may be necessary to carry out your affairs when you no longer have capacity to do so. 

A Guardian is a person lawfully invested by Court Order with the power, and charged with the duty, of taking care of the person and managing the property and rights of another person, who, for defect of age, understanding, executive functioning or self-control, is considered incapable of administering his/her own affairs.  This requires a Court process which could be cost prohibitive.