One of Facebook's first 10 employees initially rejected the job offer

Kevin Colleran was one of Facebook's first ten employees. But when Sean Parker offered him the job as Facebook's first ad salesman in 2004, Colleran turned him down.

Colleran graduated from Babson College, an entrepreneurial school in Boston, and he wanted to work for himself. Parker had gotten Colleran's name from James Hong, the creator of Hot or Not, who connected them over email.

During their first phone call, Parker asked if Colleran wanted to join and receive a "substantial share of equity" and work for a "then-unknown genius named Mark Zuckerberg."

Colleran said "no," a decision he says seemed obvious.

He explained his rationale to the 2015 graduates of Babson on Saturday during a commencement speech. Colleran gave the 13-page transcription to Business Insider Saturday afternoon and has since published it on Facebook.

"Why WOULD I say yes? I was an entrepreneur!" Colleran said. "That meant being my own boss. There was no way an entrepreneur could be anything other than his or her own boss, and I was convinced of it."

Colleran suggested Parker hire his company, Kevin Colleran Inc., to do contract work for Facebook, selling ads for it and a number of other clients. He'd only take commission, not a salary or any equity.

Luckily for Colleran, Parker pushed back.

"[Parker] explained that eventually, this small company, called Facebook, would grow large enough to where it would need to build its own sales team internally," Colleran said. "And as a third-party reseller like I had proposed, the better I did the sooner I would be obsolete-which means my new "company" would quickly grow itself out of business."

Parker's logic convinced Colleran to join Facebook, a decision that made him extraordinarily wealthy.

It's not clear how much stock Colleran had by the time he left Facebook in 2011. But judging by other early Facebook employees' outcomes, it was probably a lot. For example, Facebook's 30th employee, Noah Kagan, would have made more than $150 million from his early Facebook stock options had he not been fired before they vested.

Working for Facebook taught Colleran that you can still be an entrepreneur, even if you don't own the business you're employed by.

"I controlled my own schedule, I owned my client relationships, I built my own sales materials, and my level of effort directly impacted the amount of commission I received," Colleran told the Babson students. "I was my own boss."

Now he's the co-founder of a $65 million startup investment firm, Slow Ventures, which has invested early stage companies like Yik Yak, Meerkat, Hinge, Product Hunt and Slack.

Here's Colleran delivering the commencement speech on Saturday: