Nongovernmental health agencies are funded primarily by:

Nongovernmental agencies or organizations (NGOs) are organizations that are independent of the government and are usually nonprofit. Nongovernmental health agencies are organizations that participate in the delivery of public health services.
Nongovernmental health agencies are funded primarily by private donations. 

Nongovernmental health agencies are funded primarily by private donations. Since the health agencies are not owned by the government they will not receive money from them. These donations can come from sponsors, or patients. The health agency may not make enough money to sustain themselves, so the donations are very key to keeping them afloat.