Though not majority partners, the Sáenz-Díez Garcías emerged as the most influential branch of all the Simeón García descendants, holding some 30% stakes in the family conglomerate. Juan was from his youth being prepared to enter the business. Having reached the legal age, in 1923 he was registered as member of the board of Hijos de Simeón García de Santiago SRC and Hijos de Simeón García S.A, two companies forming part of the family retail group; it is not clear what exactly his role was. In the late 1920s he lived in the United States, getting familiar with the New York stock exchange; the heirs of Simeón García lost some $1m during the Wall Street 1929 crash. Back in Spain he resumed duties in other family companies, though he attempted also to start his own business; he launched a manufacturing company Iría S.A. and in the mid-1930s became president of Coloniales Sáenz-Díez S.A., an enterprise trading in colonial and overseas goods.