There is a lot of opportunity for nurses doing private duty. Nursing care, as defined by most nursing practice acts, follows the nursing process to include nursing assesment, nursing diagnosis, nursing intervention, nursing outcomes. This represents the independent domain of nursing. A nurse can arrange with a client privately to provide personal care, assistance with mobility, assistance with meals and anything else that the nurse is prepared for by virtue of education and licensure. The nurse should outline this in the Nursing Care Plan.
It's important for the professional to know their abilities and limitations, but then there is no problem. (Like if the patient has a fever of 102, an LPN would probably refer patient to his MD. A NP taking care of the patient at home might be able to order cultures and prescribe an antibiotic).
Anything that requires MD orders (medications, medical treatments that require a MD order, lab draws, etc) are included in a Physician's Plan of Treatment. This document is usually done by the nurse and signed by both the nurse and MD.
This is briefly how it works. I suggest you check ou the National Association of Independent Nurses (www.independentrn.com
and become a member, attend a seminar if you can. They can be very helpful with helping you get started. It really isn't that difficult to get going. Good luck.