What is the theme of the story "Lunch Money"?

“Lunch Money” proposes the idea that a young person can accomplish as much as an adult through hard work and determination. Greg embodies the young entrepreneur that has a knack for making money through various means. From doing chores to helping around his neighborhood, Greg is motivated to do whatever it takes to make money. He begins to expand his operation to selling candy, toys, and books in elementary school, occasionally facing opposition from the principal.
But by the sixth grade, Greg has to deal with competition from Maura, who started making books around the same time Greg started selling his first comic book. As Greg’s childhood rival, Maura intimidates Greg through her similar entrepreneurial pursuits. Tension initially rises between the two when they confront each other about their products, but they eventually see the value in each other and decide to work together. By putting their heads together, Greg and Maura put aside their differences to accomplish things that they couldn’t have done separately.