Citizenship by investment (CBI) programs, which grant citizenship in exchange for financial contributions to a country, have proliferated over the past decade. Where only Saint Kitts and Cyprus had formal programs in 2012, today they are found in more than ten countries. Based on three years of fieldwork, this paper dissects the challenges that emerge and how they are confronted when a sovereign function, granting citizenship, is marketized. Theoretically, it specifies the distinct properties of citizenship as a commodity and identifies the internal and external determinants of its value. Empirically, it traces how discretionary grants of citizenship in peripheral states and investment residence programs in core states conditioned the development of formal CBI schemes, and it specifies the role of geopolitical disparities, industry actors, and extra-territorial rights in this change. It concludes by assessing program outcomes and the complex ways that inequality structures the market.