I see my job as not to just deliver a product, but to help my client be successful. If I do not believe that my help will help make my client successful -- e.g.

I see my job as not to just deliver a product, but to help my client be successful. If I do not believe that my help will help make my client successful -- e.g. make money, get investment, or satisfy a contract with one of their customers -- then I typically pass. An idea validation project is not good or bad by itself, but it is often followed with other problems with the project. For example, I have had first-hand experience with the following: + If a project is unsuccessful in a business sense, many clients will blame you, even if you deliver a perfect product. + If a client is bootstrapping with his own money (or friends/family), then the client will often try to get as much out of you as possible for as little as possible. + If a client does not listen to your recommendations and you feel it is irrational, you may find the client hard to work with. + If a client wants a "kitchen sink" product and often tells you things will be "easy", then the client may have unrealistic expectations for you too and/or continually want revisions. Note that the core problem with many of these is that the client has a small budget and/or does not respect your time/work. If you can ensure that these are not problems, it is probably safe to proceed hourly/weekly but not for a flat rate.