Q: How much does a power of attorney cost?
A: Getting a durable power of attorney for finances, sometimes referred to by the initials, "DPOA" can be at no charge. Most states have the form available online, or it can be obtained through Legal Aid offices, or elder legal services providers.
In some instances, however, the matter is complicated and a lawyer's advice is needed. In those matters there may be a conflict about who should be appointed as the "agent" on the power of attorney form. If there are several siblings, we don't normally recommend putting everyone's name on the document as sharing the role of agent for the aging parent. It can lead to family conflicts.
In your case, your mother wants to appoint you, and as long as she is sufficiently clear in her thinking to understand what she is doing, there is no problem with her doing so. The form gives unlimited control over her money to you, and it is therefore very important that she is aware that you will have the legal authority to decide everything about her finances, including where she will live, who will take care of her, and how her money will be spent if she is unable to speak for herself.
There is sometimes confusion about what the term "power of attorney" means. In this answer, I am referring only to the document that lets your mom give you control over her money.
There is another form, sometimes called "medical power of attorney" or health care directive or living will that is different from the financial power of attorney. That health care directive has nothing directly to do with money decisions. It gives authority to a person to make medical decisions if the elder can't speak for herself. The agent on a health care directive does not have legal authority to decide anything about money.
If your mom is considering appointing you her agent for a durable power of attorney for finances, it might be good to discuss if she also wants you to be her agent for health care decisions, in the event that she is not competent at some point to make those decisions. These are two separate documents, but often are prepared at the same time. The healthcare directive is also free, and is available from your mom's doctor, clinic, or hospital, and is usually free as a downloadable form online as well.