Trading can rival any of the other careers in EVE, both in how lucrative it can be and the amount of risk involved. You can make a billion ISK in a few days and lose it all instantly. While anyone who buys and sells on the market for profit can call themselves a trader, only after mastering a few secrets can you truly be a successful trader.
Profitable deals in EVE can appear instantly and disappear just as fast. You must take account of the amount of time it will take you to transport your goods whenever you are considering a trade route. The profitable deal that you just found 15 jumps away may well be gone by the time you get there. A trade route that makes you 100 million in one hour is less profitable than the trade route that will make you 20 million in ten minutes.