At the beginning of the play, Walter and Beneatha's father has recently died, and Mama (Lena) is waiting for a life insurance check for $10,000. Walter has a sense of entitlement to the money, but Mama has religious objections to alcohol and Beneatha has to remind him it is Mama's call how to spend it. Eventually, Mama puts some of the money down on a new house, choosing an all-white neighborhood over a black one for the practical reason that it happens to be much cheaper.
Later she relents and gives the rest of the money to Walter to invest with the provision that he reserve $3,000 for Beneatha's education. Walter passes the money on to Willy's naive sidekick Bobo, who gives it to Willy, who absconds with it, depriving Walter and Beneatha of their dreams, though not the Youngers of their new home. Meanwhile, Karl Lindner, a white representative of the neighborhood they plan to move to, makes a generous offer to buy them out. He wishes to avoid neighborhood tensions over the interracial population, which to the three women's horror Walter prepares to accept as a solution to their financial setback. Lena says that while money was something they try to work for, they should never take it if it was a person's way of telling them they weren't fit to walk the same earth as they.
Meanwhile, Beneatha's character and direction in life are being defined for us by two different men: Beneatha's wealthy and educated boyfriend George Murchison, and Joseph Asagai. Neither man is actively involved in the Youngers' financial ups and downs. George represents the "fully assimilated black man" who denies his African heritage with a "smarter than thou" attitude, which Beneatha finds disgusting, while dismissively mocking Walter's lack of money and education. Joseph patiently teaches Beneatha about her African heritage; he gives her thoughtfully useful gifts from Africa while pointing out she is unwittingly assimilating herself into white ways. She straightens her hair, for example, which he characterizes as "mutilation."
When Beneatha becomes distraught at the loss of the money, she is upbraided by Joseph for her materialism. She eventually accepts his point of view that things will get better with a lot of effort, along with his proposal of marriage and his invitation to move with him to Nigeria to practice medicine.
Walter is oblivious to the stark contrast between George and Joseph: his pursuit of wealth can be attained only by liberating himself from Joseph's culture, to which he attributes his poverty, and by rising to George's level, wherein he sees his salvation. Walter redeems himself and black pride at the end by changing his mind and not accepting the buyout offer, stating that the family is proud of who they are and will try to be good neighbors. The play closes with the family leaving for their new home but uncertain future.
The character Mrs. Johnson and a few scenes were cut from the Broadway performance and in reproductions due to time constraints. Mrs. Johnson is the Younger family's nosy and loud neighbor. She cannot understand how the family can consider moving to a white neighborhood and jokes that she will probably read in the newspaper in a month that they have been killed in a bombing. Her lines are employed as comic relief, but Hansberry also uses this scene to mock those who are too scared to stand up for their rights. In the introduction by Robert B. Nemiroff, he writes that the scene is included in print because it draws attention away from a seemingly happy ending to a more violent reality inspired by Hansberry's own experiences.
more information about this play's history https://en.wikipedia.org/wiki/A_Raisin_in_the_Sun