How does Paul Edward buy the land in Roll of Thunder, Hear My Cry?

In Chapter Four, Big Ma tells Cassie about marrying her husband, Paul Edward, who had been born a slave in Georgia and who was working as a carpenter in Vicksburg when she met him. They bought their first two-hundred acres of land from a Yankee named Mr. Hollenbeck who had bought it during Reconstruction from the Grangers, and the second two-hundred acres from Mr. Jamison, who was a lawyer. Harlan Granger has always wanted to buy back all the Granger land but Paul Edward wouldn't sell it. Their two daughters died as babies, their son Mitchell died in World War II, and their son Kevin drowned, and now the land is Big Mama's, Cassie's father's, and her son Hammer's. She says that she will never sell it.