common experience of billionaires

Achieving Billionaire Status Takes Time.
The average Forbes billionaire is 63 years old, and more than 90% are over the age of 45. There are some notable exceptions to the rule as younger people are joining the ranks, generally because of products and services now possible through technological advances.

 More than 30% of the wealthiest people on the Forbes list have no college degree including Bill Gates (Microsoft, number one on the list) and Zuckerberg (both Harvard University dropouts). Michael Dell (Dell Inc., University of Texas at Austin), Steve Jobs (Apple, Reed College), and Larry Ellison (Oracle Corporation, University of Chicago) also failed to graduate from college.

Family Money Helps, But Is Not Critical.
 60% made their wealth themselves, including Gates, Buffet, and Ellison, whose families were middle-class,About 15% are billionaires from their inheritances.

Careers in Tech, Finance, or Real Estate Can Pay Off Big. 
The source of wealth for many billionaires is their development of a disruptive technology and going mainstream through a public offering of their company. For example, Microsoft (Gates, Paul Allen, and Steve Ballmer), Google (Larry Page, Sergey Brin, and Eric Schmidt), Amazon.com (Bezos), and Facebook (Zuckerberg) are companies made possible only by new technology.