Volunteer

Someone who works for the good of others without pay or with minimal pay,It is a French word, some times meaning "will"
Volunteering comes in many forms: serving food at the local homeless shelter, providing computer technical support to a non-profit organization, acting in a leadership capacity on a charitable organization's board of directors or coordinating the emergency response in the case of a disaster. Around the world volunteer centers exist to support the voluntary sector and make a difference in the communities that they serve.
Funny enough, some volunteer earn more than regular workers from poor countries