Oh! We just covered this unit, so I can help you here!
So, just like slavery, sharecropping was a cheap way to get labor. The only difference was that the white people had to actually pay the laborers. It also made it hard for blacks to escape from sharecropping, as the black codes said they must work, but basically banned every other form of work. It also said they MUST be employed by a white person at all times.
Hope this helps! Have a great day!