Dr. Gomez is retiring as a doctor in private practice. He wants to start a(n) , Doctor Help, that will provide low-income individuals in the United States with medical assistance at no cost.

Nonprofit organization.

Explanation:

As the exercise hints, what Dr. Gomez aims to start is a nonprofit organization (NPO); which is a non business entity whose aim is to help a particular movement, social cause, etc. His goal is to help low-income individuals in the United States with medical assistance at no cost with an NPO called "Doctor Help", who would kindly help those in need that can't afford medical aid otherwise. What characterises an NPO is that they do not keep the surplus of money that they receive, but they re-invest it until they achieve their goal, they do not aim to make a profit.