Indentured Servants

"Between one-half and two-thirds of white immigrants to the American colonies between the 1630s and American Revolution had come under indentures.[2] However, while almost half the European immigrants to the Thirteen Colonies were indentured servants, at any one time they were outnumbered by workers who had never been indentured, or whose indenture had expired, and thus free wage labor was the more prevalent for Europeans in the colonies.[3] 

Indentured people were numerically important mostly in the region from Virginianorth to New Jersey. Other colonies saw far fewer of them. 

The total number of European immigrants to all 13 colonies before 1775 was about 500,000; of these 55,000 were involuntary prisoners. Of the 450,000 or so European arrivals who came voluntarily, Tomlins estimates that 48% were indentured.[4] About 75% of these were under the age of 25. 

The age of adulthood for men was 24 years (not 21); those over 24 generally came on contracts lasting about 3 years.[5] Regarding the children who came, Gary Nash reports that "many of the servants were actually nephews, nieces, cousins and children of friends of emigrating Englishmen, who paid their passage in return for their labor once in America."[6]

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https://en.wikipedia.org/wiki/Indentured_servitude

How long did indentured servitude last?

four to seven years

Servants typically worked four to seven years in exchange for passage, room, board, lodging and freedom dues. While the life of an indentured servant was harsh and restrictive, it wasn't slavery. There were laws that protected some of their rights.

Indentured Servants In The U.S. | History Detectives | PBS