What should we know before agreeing to hold a power of attorney?

A family member has asked my husband to hold her power of attorney. She has been fighting alcohol addiction for quite a while, has alienated her children and a lot of her family, and has hit her bottom. We are gathering information on what this would entail. I am wondering what advice the Collective might have for someone considering holding a power of attorney. As far as we understand it would be a financial and a healthcare POA.