Joseph Süss Oppenheimer (1698-1738) is best known for the spectacular show trial that led to his execution and for the antisemitic afterlives of his figure. Scholarship has therefore long focused on the trial and its political and cultural meanings. Much less attention has been paid to Oppenheimer as an actor within the Jewish world of his time. This paper presents findings from an ongoing dissertation project based on previously neglected Yiddish and Hebrew sources, especially business letters. These texts allow for a new perspective on Oppenheimer's economic and social practices before the trial and on his embeddedness in intra-Jewish networks of trust, credit, information, and reputation. By reading these letters alongside German-language account books and correspondence, the paper reconstructs Oppenheimer's ego-network and examines how he navigated the structural limitations imposed on Jews in early eighteenth-century German territories. It argues that Oppenheimer's strategies did not simply consist in assimilation or "escape" from Jewish society, but rather in a selective and situational use of both Jewish and non-Jewish social worlds. Yiddish and Hebrew offered spaces of communication that were more intimate, flexible, and culturally coded, and thus essential to his economic success. The paper thus reframes Oppenheimer not as an isolated exception or mere victim of political intrigue, but as a highly skilled broker operating between overlapping social, legal, and religious regimes. In doing so, it contributes to broader debates on minority agency, economic integration, and the social history of early modern Judaism.