I have been temporarily housing my 15 year old nephew who has been repeatedly kicked out of his home by his mother. She is willing for him to live with me but refuses to verbally speak to me. Would a power of attorney be valid in California to legally have my nephew so that I can enroll him in school, get Medical for him, and to legally claim him as a dependent? The mother said she would sign a notarized letter stating that I have custody of her son but I want something a little more legal, which made me think of a power of attorney. Also, I heard that applying for a guardianship is very costly, another option. Thanks for any help with this question.