You need to feel the passion of a founder and be 100% on board. Angel investor David H. Page, a specialist in business development for startups, told Business Insider that anyone thinking of working for a founder should find out about the founder's purpose, history with startups, successes, failures and, most importantly, whether they can inspire others.
Gather as much information as you can to get a sense of the founder's vision, their style, and their goals. If you are not in sync with the founder, you may be setting yourself up for frustration and conflict working with this startup.