There are now strict regulations in place in the form of RERA for unscrupulous marketing practices. However TN has not yet notified the rules so that is a risk.
Binny is a landowner and i dont think will be involved in the sales & marketing of the project but it needs to be verified.
Agreements are mandatory within a defined time period after booking and no developer nowadays takes the risk of concluding a sale without an agreement in place. Real estate practices are going through a seismic shift in India and the bad developers & customers will be weeded out in time.
Different investors have different views about discount rates - in the end its the inherent risk that you sense in the investment that determines the expected return. I apply 13% for low risk opportunities.
If you are applying say 15% or more it indicates that you perceive the opportunity as risky and then you shouldn't be in the stock in the first place regardless of the risk reward ratio!