How does Gatsby really earn his money?

Gatsby earns his money through a combination of questionable business ventures, including bootlegging alcohol during Prohibition and engaging in other illicit activities. While he presents himself as a wealthy and respectable figure, much of his fortune is shrouded in mystery and derived from illegal sources. His ostentatious lifestyle and lavish parties serve as a façade to mask the true nature of his wealth and the lengths he goes to in order to win back Daisy Buchanan.