In his 2017 return, O’Rourke reported an adjusted gross income of $366,455. He also reported that he paid $81,019 in taxes.
In August, Forbes estimated O’Rourke is worth $4 million.
Meanwhile, GoBankingRates.com estimates his net worth ranges between $3.42 million and $16.36 million, with most of his income coming from real estate.
O’Rourke also makes money from a stake in his software and technology company, as well as his wife, Amy’s trust fund, according to The Texas Tribune.
Amy, who is part of an educational nonprofit in El Paso, is the daughter of William Sanders, who is estimated to have a net worth of about $500 million, according to Forbes -- though The New York Times had previously called Sanders a billionaire.
O’Rourke and his wife started their IT company, Stanton Street Technology Group, back in the 1990s Business Insider reported in 2013, when he was first elected to Congress.
According to his 2017 financial disclosure report for the House of Representatives, he and his wife made between $100,001 and $1 million in capital gains from Stanton Street
However, the form also showed that Amy sold her stock in the company in March 2017 for somewhere between $250,001 and $500,000.
O’Rourke represented Texas in the House of Representatives from 2013 to 2019 and last year, ran an unsuccessful Senate race against Sen. Ted Cruz.
Despite the loss, his Senate campaign raised $80.3 million, which is the most a Senate candidate has ever raised during one election, according to the Center for Public Integrity.
O’Rourke decided to join the 2020 presidential race in March.
Fox News’ Paul Steinhauser contributed to this report.