And people off the books or a student?
Lol, I was joking.
Seriously speaking, if you're over 21, you can include any income that can be counted upon to pay the bill. If you are supported by others, you can put down their income. This includes household income for many of the students here on DDF, and probably the shver for a chunk too. The only ones that may ask you to verify your income after approval is amex (commonly known as an FR, or financial review). Many people pass those, even with tax documents that show less income than reported (albeit with spending limits imposed).
If you default on your bills, and your income reported was completely fraudulent, then there was a story of a bank that pursued criminal action. This is incredibly uncommon, highly unlikely to happen if you pay your bills, and not a problem if you're reporting existent income, even if it's not your own.