Why did Miguel de Cervantes make little money from Don Quixote?

Miguel de Cervantes made little money from the first part of Don Quixote primarily because he sold the publishing rights to the bookseller Francisco de Robles for an unknown sum in 1604. By selling these rights, Cervantes relinquished any future financial profit from the sales of that volume.1

Because he did not retain ongoing royalties, Cervantes had to rely on patronage to supplement his income, dedicating his works to influential figures such as the conde de Lemos and the archbishop of Toledo to improve his financial circumstances. Despite the novel's immediate and widespread success, Cervantes remained in a state of relative financial struggle throughout his life, often plagued by litigation and the need for steady employment, which he had previously sought as a commissary of provisions.12