... the basement income to qualify as 'rich' will here be 
  considered to be $400,000 in annual income that'll come in 
  regardless of whether anyone in the family is holding a 
  paying job or not.

From "What are your TRUE chances of getting rich in America? OR How to get rich in America"[1]

You might also be interested in "The super-rich, the 'plain' rich, the 'poorest' rich... and everyone else"[2].

[1]: http://www.jmooneyham.com/your-true-chances-of-getting-rich.... [2]: http://www.jmooneyham.com/rich.html