Actually, most of Barak's money comes from the books he wrote; the one he wrote in 1995 Dreams from my Father, and the Audacity of Hope which he wrote after his 2004 Democrat National Convention speech.

He got a $1.9 million advance on The Audacity of Hope but the real money came when he ran for President:

In 2006 he got $147,490 for "Dreams From My Father" and $425,000 from Random House for "The Audacity of Hope." In 2007, as his presidential run made him a household name, book sales skyrocketed. He got $815,971 for Dreams and $3.28 million for Audacity.

The income continued, and he mostly put the money into U.S. Treasury Bills:

By the time he was sworn in, Obama owned somewhere between $1.1 million and $5.1 million worth of U.S. Treasury Bills, comprising most of his net worth. His other assets were worth between $411,000 and $915,000... [a lot of that is in] Vanguard FTSE Social Index Fund, which invests based on "certain social, human rights, and environmental criteria."

He donated all of his $1.4 million in Nobel Prize money to charities:

$250,000 to Fisher House, which gives free housing to veterans and military families getting medical treatment.

$200,000, plus any remaining unallocated money, to the Clinton-Bush Haiti Fund of the Clinton Foundation, a fund that helped rebuild Haiti in the aftermath of the devastating earthquake.

$125,000 to the American Indian College Fund, which gives scholarships to Native Americans.

$125,000 to the Appalachian Leadership and Education Foundation, which gives scholarships to low-income residents of the Appalachia region.

$125,000 to College Summit, an organization that aims to raise college enrollment rates.

$125,000 to the Posse Foundation, which provides full scholarships to extraordinary high school students.

$125,000 to the Hispanic Scholarship Fund, which gives scholarships to Latino students.

$125,000 to the United Negro College Fund, which gives scholarships to Black students.

$100,000 to Africare, an organization that builds wells and treats disease in Africa.

$100,000 to the Central Asia Institute, which focuses on education and public health, primarily for girls in Central Asia.

Now he earns $400,000 a year to be President.

Obama's net worth is estimated at between $2.8 million and $11.8 million. (That's a big range, but you get the point. He isn't hurting.)

Read more.

The guy is the biggest celebrity in the world, and has less cash than a lot of engineers at Facebook. I think that shows pretty convincingly that he's NOT doing this for money.