Public sector unions are powerful political actors in the Mexican public sector at the federal, state, and local government levels. This study intends to understand two long-standing practices unions engage in: the selling of public positions and the inheritance of public positions. Through an exploratory qualitative approach, this study intends to understand the mechanisms that sustain these personnel practices: What are the mechanisms involved, what functions do they serve, and how are they sustained? We find that practices are normalized, reproduced, and systematized, at times representing a gross misappropriation of public resources (selling) that prey on the needs of people who do not have connections and are desperate for jobs, or serve as a safety net for certain groups (inheritance), and as political capital for politically powerful groups, including unions and politicians who directly promote these practices. Understanding the persistence of these practices that clash with the conception of modern bureaucracies contributes to understanding the variety of patrimonial practices that are present in the Mexican public sector and helps identifying the challenges and the opportunities that these practices might provide.