1) Some, unable to pay their mortgages, lost their plantations when the banks foreclosed. Some sold out to Northern carpetbaggers. Those who were able to keep their land realized that they could not sustain cotton production on an industrial scale without the slave labor force, because they could not afford to pay living wages. They developed a system called sharecropping by which the field hands would receive a portion of the crop in exchange for their labor. The sharecroppers lived on the plantation in their own shacks. In practice, the system was little better than slavery. the sharecropper had to pay their rent out of their share of the crop, with very little left over for anything beyond subsistence.
2) Because, as with most wars, it was funded and run by the rich but the fighters on the front lines were often poor farmers and other middle class civilians. Poor whites had to compete with freedmen for the few available jobs. Unable to find work, many chose to migrate.
[hope this helped!]
