As everyone seems to agree, you're being contracted to build a web app for the client. The business model and marketing behind it, is essentially his challenge

As everyone seems to agree, you're being contracted to build a web app for the client. The business model and marketing behind it, is essentially his challenge. > I'm not sure that in all good conscience I can take on a project that is going to cost him a lot of money and not be successful. No one can ultimately say a project will be successful or not as there have been good ideas that died, and bad ideas that took off. Take the money, build the best web app that you can build.