Just a fack check.

There is at least one person who have worked for others and becomes a billionaire because of that: Charles Simonyi. (http://en.wikipedia.org/wiki/Charles_Simonyi). But he is probably the only 1 in 6,697,254,041 human beings who achieve billionairehood by working for others.

And yes, he worked one time in Xerox PARC before Microsoft.