What did Vanderbilt use to buy out
other companies?

Cornelius Vanderbilt (May 27, 1794 – January 4, 1877) was an American business magnate who built his wealth in railroads and shipping.[2][3] After working with his father's business, Vanderbilt worked his way into leadership positions in the inland water trade and invested in the rapidly growing railroad industry. Nicknamed "The Commodore", he is known for owning the New York Central Railroad.