More than the money, what matters is what it means for all the Youngers’ lives, a subject with multiple dimensions. The answer is connected to the poem that gives the play its name, with Langston Hughes’ question: What happens to a dream deferred?

In Act II, Scene II, Walter Lee Younger and his mother, Mama, disagree about how to spend the insurance money that she has just received, following his father’s death. When Walter returns home from work and learns that the check has arrived, Mama tells him immediately that she will not use it for the liquor store he wants to open with two friends. Walter is furious, and argues with his mother, who challenges him on his anger and apparent obsession with money. When he denies anything is the matter, she says

Something eating you up like a crazy man. Something more than me not giving you this money.

Walter first denies it, then says it’s about what the money can do for them, and tells her of his desires for himself and his family.

Mama—Mama—I want so many things . . . I want so many things that they are driving me kind of crazy . . .

Walter finds it difficult to explain just why this is such a problem. Much of the answer to the question you pose actually can be found in the previous scene: first, when he is arguing with Ruth, his wife, and Beneatha, his sister, about the insurance money; and second, when Ruth and Mama are conversing after he leaves for work. He is frustrated that he is misunderstood and has achieved so little, and that the family is living in a small apartment.

This morning, I was lookin’ in the mirror and thinking about it . . . I’m thirty-five years old; I been married eleven years and I got a boy who sleeps in the living room—(Very, very quietly)—and all I got to give him is stories about how rich white people live . . .

Later, Mama reminisces about his father, Big Walter, used to say,

Seem like God didn’t see fit to give the black man nothing but dreams—but He did give us children to make them dreams seem worthwhile…. [He was] a fine man—just couldn’t never catch up with his dreams . . .

Walter’s frustration comes from worry that, like his father, he will not be able to catch up with his dreams. In Scene II, he tells her what he imagines:

The future, Mama. Hanging over there at the edge of my days. Just waiting for me—a big, looming blank space—full of nothing. Just waiting for me.

Walter is caught in a world where he has a job, a wife and child and still lives with his mother who considers herself the head of the family. He believes that neither Ruth, his wife, nor Mama, considers him trustworthy and "grown-up enough" to handle responsibility. Neither one on them really listens to his dreams so he feels that he has no real control of his life. That is why he so desperately wants to invest the insurance money in the liquor store. Walter feels that having his own business will at least give him some control over his life. Mama finally realizes that also when she gives him the money that is left after she buys a house. Walter does end up losing the money, but he gains his self respect when he refuses Linder's offer. To Mama, and to Lorraine Hansberry, self respect is even more important that money.