There are two primary divisions of professional day traders: those who work alone, and/or those who work for a larger institution.
Most day traders who trade for a living work for large players like hedge funds and the proprietary trading desks of banks and financial institutions. These traders have an advantage because they have access to resources such as direct lines to counterparties, a trading desk, large amounts of capital and leverage, and expensive analytical software.
These traders are typically looking for easy profits from arbitrage opportunities and news events. Their resources allow them to capitalize on these less risky day trades before individual traders can react.