The dreams, hopes and plans of the characters in The House on Mango Street are often symbolized by a house – check out our discussion of houses in this novel in the "Symbolism, Imagery, Allegory" section for more on this. For Esperanza's Mama and Papa, the idea of happiness and security is summed up in the image of a white house, big enough for their whole family. They pass this dream down to their children, but Esperanza takes it and makes it her own – her dream becomes having a house all to herself, in which she can be free to write.
Solitude is an essential component of Esperanza's plans for the future – without a space to call her own, she'd be unable to fulfill her goals of being a writer.
Social activism has always been a part of Esperanza's dreams and hopes, though she doesn't realize it until the end of the book. When Esperanza says she "won't forget who [she is] or where [she] came from," and pledges to let bums stay in the attic of her dream house, she's envisioning doing her part to create a better society.