This document discusses how an understanding of development economics is important for planners. It explains that plans need to be financially feasible and consider the marketplace in order to be implemented. It also outlines various types of market and financial feasibility studies that planners can use to ensure plans will work from an economic perspective. Key concepts covered include return on investment for developers, factors that impact feasibility, and how the role of planners is shifting to be more market-savvy and focus on transformational planning.