Ben & Jerry’s was started by childhood best friends. Four grad school buddies founded Warby Parker. A long friendship-turned-partnership brought Clear to TSA security lines across the U.S.. A shopping trip between two pals launched size-inclusive clothing brand Universal Standard. Yes, stories of successful business partnerships between friends exist. But for every Ben and Jerry, there are countless Janes and Joes ticked off at their college roommate for stiffing them on a business loan. Mixing business and friendship can tank a relationship. So, if a classmate, colleague or childhood friend asks you to invest in their business, you need to look at it from all angles. Think Like a Professional Investor Don’t let your personal relationship cloud your business judgment. Evaluate the request as if it was coming from a stranger. Does the business offer something unique? Does it fill a need in the market? Does the founder have business …