How did the southern whites regain political power during reconstruction

Abraham Lincoln was assassinated and the South put in a system called "Black Codes" where you had to train to be on a farm and you couldn't leave until the owner said you were ready. And, unemployment was illegal. and you were fined. But how were you going to pay for that money? they then send you to work for a wage on a farm to pay back the government. but it's not like slavery were they get free food and a place to sleep. you have to pay for all of that. and by the end of the day, you spend as much as you earn on just being alive, while never being able to pay back the government.