When eBay buys your company for $1.5 billion, you might consider spending the rest of your days sipping cocktails on the beaches of Silicon Valley (or just go ahead and buy the beaches themselves). But that's not what these seven former PayPal colleagues did. Instead, the so-called PayPal Mafia went on to invest in so many of the same wildly successful private tech startups that The New York Times had to map it out.

Take a look at the billion-dollar boys club below:

  • Peter Thiel, one of PayPal's co-founders and the company's former chief executive, has invested in four of the most valuable tech companies in Silicon Valley: Airbnb (valued at $40 billion), Palantir ($15 billion), SpaceX ($12 billion), and Stripe ($3.5 billion). Thiel was also one of the earliest investors in Facebook.
  • Jeremy Stoppelman, PayPal's former vice president for engineering, similarly invested in Airbnb and Palantir as well as Square, Uber, and Pinterest.
  • Keith Rabois, PayPal's former head of business development and current partner at Khosla Ventures, previously held executive roles at LinkedIn and Square and now holds shares in Airbnb, Stripe, and Palantir.
  • Elon Musk, who co-founded the company that became PayPal, went on to launch SpaceX (now worth $12 billion) and Tesla (worth $23 billion). Oh, and he also invested in Stripe.
  • Scott Banister, a former PayPal board member, co-founded email service IronPort, which sold to Cisco in 2007 for $830 million. Banister has also invested in Uber and SpaceX.
  • Max Levchin, PayPal co-founder and its former chief technology officer, sold social gaming company Slide to Google in 2010 for $182 million and recently started online payments company Affirm. Levchin also has stakes in Pinterest and Stripe.
  • Roelof Botha, former PayPal head of business development and current partner at Sequoia Capital, has investments in Square.

The undeniable presence of former PayPal executives within Silicon Valley's tech landscape goes even deeper than just the big seven. LinkedIn, now worth $31 billion, was co-founded by former PayPal chief operating officer Reid Hoffman. Stoppelman and lead software architect Russell Simmons co-founded Yelp, worth $3.51 billion. In 2006, Steve Chen, Chad Hurley, and Jawed Karim--all PayPal alum--founded YouTube, which was acquired by Google for $1.6 billion. So how is it that one dot-com-era company continues to churn out billion-dollar success stories?

One part of the equation is that "success begets success," the Times notes.

"There's a network effect to these things," Yelp CEO Jeremy Stoppelman tells the Times. "If you have a name that's associated with success, people will seek you out. Why do smart people go to Harvard? Because previous smart people went to Harvard."

The second part of the equation is slightly more feasible for most entrepreneurs but nonetheless vital for setting up your business for industry domination at the get-go. In his book Zero to One, Thiel identifies seven questions that every business must answer if it hopes to reach the same level of success as PayPal:

  1. The Engineering Question: Can you create breakthrough technology instead of incremental improvements?
  2. The Timing Question: Is now the right time to start your particular business?
  3. The Monopoly Question: Are you starting with a big share of a small market?
  4. The People Question: Do you have the right team?
  5. The Distribution Question: Do you have a way to not just create but to also deliver your product?
  6. The Durability Question: Will your market position be defensible 10 and 20 years into the future?
  7. The Secret Question: Have you identified a unique opportunity that others don't see?

Check out an Inc.com article by Bill Carmody, founder and CEO of marketing services provider Trepoint, to learn how to ace each of these seven steps.