The objective of this study is to study financial feasibility of housing estate and single-detached housing project in Phra Nakhon Si Ayutthaya province. Also to study the sensitivity of the single-detached housing project in Phra Nakhon Si Ayutthaya by using primary and secondary data from interviews with housing development project owners and its sales staff in Ayutthaya province. Financial feasibility study results reaffirmed that the project will worth your investment. If calculated, the project will have a net present value of 50,709,383 baht which is greater than zero, 8.48 percent of internal rate of return (IRR) which is greater than the weighted average cost of capital (WACC), 1.08 benefit-to-cost ratio (BCR) which is greater than 1. As long as the cost increases but not more than 8.88 percent and the return on investment decreases but not more than 8.15 percent - this project is established to be worth investing in.