Middle-class Joe, no mo'...

Joe Biden once described himself as the poorest man in the United States Senate, but financial records now paint a very different picture. In the two years following leaving office as vice president to Barack Obama, Biden and his wife made $15 million, according to a report published this summer in the Washington Free Beacon.

According to the Free Beacon, Joe and Jill Biden's income totaled approximately $390,000 by the end of the Obama administration. However, by the end of 2018, the Bidens' tax return reported an adjusted gross income of almost $4.6 million, a step down from the $11 million the couple made in 2017. The two are said to have a net worth of approximately $9 million, according to Forbes.

The focus on Biden's finances come as news of his son Hunter Biden's questionable business dealings in Ukraine have become public knowledge. The younger Biden served on the board of Burisma, an energy company that Ukrainian prosecutors suspected was engaged in fraudulent activity. Hunter Biden had no energy industry experience prior to accepting the position where he was paid hundreds of thousands of dollars.

How did they do it?

In an article published this week, Business Insider detailed how the Bidens made their wealth.

In his last year in the Senate, Biden's salary was $169,000. Thereafter, his tenure as vice president from 2009 to 2017 gave him a 30 percent raise, earning an average of $225,000 per year. Joe and Jill Biden also earned about $500,000 in pensions and social security benefits during those eight years.

Since leaving the vice presidency, Biden has made hundreds of thousands of dollars from books and speaking fees, and has even amassed a multi-million dollar real estate portfolio.

Biden invested in second and third homes after leaving office, including the purchase of a lavish $2.7 million beach-front 4,800 square-foot house in Delaware. He also rents a 12,000 square foot five bedroom, ten bathroom home in McLean, Virginia.

Millions in speaking fees and royalties

Biden made a significant amount of money from his 2017 book, "Promise Me, Dad," about his relationship with another son, Beau Biden, who died of cancer. Biden's financial disclosure forms showed he made between $8,000 to $90,000 per stop on his book tour. The Free Beacon noted that the former vice president charged $234,000 for a "VIP appearance" stop on his book tour.

According to Forbes, the sales from the book book resulted in $1.8 million for the Bidens. Additional public speaking engagements contributed $2.4 million to the couple's net worth. CNBC also reported that Biden was paid $190,000 for a March 2018 lecture at Drew University in New Jersey.