Earning while playing may sound like an impossibility, but with the advent of the Internet, people are given the opportunity to do just that. I know a friend of a cousin who is still a student, but who already earns thousands of our local currency just by creating WoW accounts and selling them to fellow WoW players who do not have enough time to advance their characters but want to play just the same.
When they buy WoW accounts from him, clients are purchasing accounts that took him a while to improve the level of, thus the justification in the price. It is easy to find sites and individuals whom you can buy WoW account from, what with the massive popularity of the game, but there are also scams abound, so always be careful when transacting online.