This Yale lecture from Creating Change through Social Entrepreneurship examines the legal structures available to founders launching a mission-driven organization. The instructor walks through the tradeoffs between operating as a nonprofit, a for-profit, a hybrid entity, or a fiscally sponsored project, and explains how each option affects fundraising, taxation, governance, and long-term flexibility. The lecture covers when it makes sense to build inside an existing organization rather than incorporate from scratch, and how legal form should follow the venture's revenue model and mission rather than the reverse. Aimed at early-stage social entrepreneurs still shaping their concept, the session gives a practical framework for matching structure to strategy before committing to paperwork. Part of Yale's broader course on building ventures that pursue social impact alongside financial sustainability.