Joining a startup is tricky business. The nature of a startup is so dynamic that what you joined a startup for may not be what you end up doing at a startup. So

Joining a startup is tricky business. The nature of a startup is so dynamic that what you joined a startup for may not be what you end up doing at a startup. So if you joined a startup for something you felt passion of, particular tech or idea. Then be wary as this may change and you might find your self working on something totally different, especially if the control is not in your hands. More importantly make sure you have worked with people or a person you are about to start a startup with because if trust/chemistry is not there then nothing of much worth can be achieved.