Warren Buffet was born in 1930 to Howard Buffett, a four-term "Old Right" libertarian Republican state rep from Nebraska. Howard unseated a Democrat in '42 and cruised to reelection opposing the New Deal and social security in '44. In high-school he invested in a brokerage company that his dad owned, and when he was 14 he used some of those earnings ($1,200 - about $17 grand in 2019 dollars) to buy a 40-acre farm run by a tenant farmer. He went to school at Wharton, University of Nebraska, Columbia and Wall Street's New York Institute of Finance. He was not in debt after all of these schools, he actually had $9,800 in savings when he graduated in 1951 (about $98,000 in 2019 dollars).
In 1956 he started the investment firm which eventually became the multinational conglomerate holding company Berkshire Hathaway, the third largest company in the world that wholly owns over 60 companies like Geico, Duracell, Dairy Queen, GenRe and BNSF. Buffett and Berkshire Hathaway also own significant minority stakes in Verisign, Kraft/Heinz, American Express, Wells Fargo, Moody's, Bank of America, Coca-Cola, Apple, Delta, Southwest, American Airlines.
He became one of the three richest men in the world by investing heavily in monopolies and near-monopolies. If you have 10 minutes and want the details David Dayen's 2018 article in The Nation breaks down a few of Buffett's most egregious investments.