Professional organizations involved with mountain rescue usually provide mountain rescue services as minor portion of their full time responsibilities. The two major types of professional orgainzations are ski patrols at established ski resorts, and national park service units.
Outside of ski resorts and national parks, most mountain rescue services in the US are provided by volunteers (for example, the Mountain Rescue Association). Mountain Rescue Association teams do not charge accident victims for rescue services.
Volunteer teams are often short of funds, and appreciate donations.