Each sprint round winner will be the participant with the highest percentage gain in his or her Game account in one day's trading on the designated day. If it's out there and has a ticker symbol, you can buy it. In the interest of fairness, players can execute a maximum of 10 trades per day. The game was designed to be lifelike. You can trade as much as you want, but just like in the real market, there's a commission charged on every trade.
Commissions vary depending on the type and size of the order.
Don't worry, you can start playing whenever you'd like. You always have a shot at the Grand Prize, and if not, there are Sprint Round prizes throughout the game. Sorry, all buys must be paid in full at the time of trade. Not in the game. Many commonly asked questions are answered on the Online help page found on the side navigation bar of all game pages.