Some of the most prolific and successful companies in history began as partnerships. Think McDonald's, Hewlett Packard, and Google. On the flip side, you have those partnerships that went down in flames. Facebook's split between Saverin and Zuckerman, Citigroup's breakup between Jamie Dimon and Sandy Weill among others. That's why it's important to do your homework, consult a professional, and don't let emotions get in the way.