The short answer is that the potential earnings from Betfair trading are unlimited. As with any business or investment, the amount you can make depends on a variety of factors, including your skill level, the amount of time and effort you put in, and the amount of capital you have to invest.
The Betfair Exchange connects you with a community of punters, allowing you to set your own odds and place bets directly. Without bookmaker intervention, Betfair fosters a real community that interacts directly with odds, offering you better value and improved odds.