How to get a power of attorney of an 18 year old?

Dose anyone know who you go to to get power of attorney medically and financially over a child who has several disabilities who is turning 18 all the Dr’s and insurence is highly recommending I do this but no one will tell me where I go what it is I need to do hiring a lawyer is not a option for me with not having the financial funds with being a single mom of multiple children