In Harper Lee's To Kill a Mockingbird, the Cunninghams, along with many other people in Maycomb, struggle financially—especially in light of the Stock Market Crash of 1929 which hit the poor the hardest, especially those in the South still attempting to recover from the ravages of the Civil War, which had only ended some sixty-five years earlier.
Atticus provides Mr. Walter Cunningham with legal assistance but Walter cannot pay for it. He pays, instead, with goods, in the old-fashioned way of bartering: goods in exchange for services. Mr. Cunningham is a proud man, and Atticus is aware of this and has no desire to make Cunningham feel embarrassed that he hasn't the cash. Atticus is very serious in his gratitude when the other man stops by to settle his "account."
Specifically, we read in Chapter Two:
One morning Jem and I found a load of stovewood in the back yard. Later, a sack of hickory nuts appeared on the back steps. With Christmas came a crate of smilax and holly. That spring when we found a crokersack full of turnip greens, Atticus said Mr. Cunningham had more than paid him.