Trading - Each of the New Eden's star systems has its own economy, which means that prices of certain goods can differ greatly from system to system.Profits that could be generated with this method vary greatly depending on your pilot skills, chosen ship, support of other players, and a few more factors, but they can easily reach millions of EVE Online ISK per hour with high-end mining vessels. The risk of getting ganked during mining is always present, but there are some module choices that can help you protect yourself. If you opt for high-sec mining, you can do it semi-AFK, but your profits will be lower than in null-sec zones (which are much more dangerous, however). Everybody can do it, and the entry cost is very low all you need is a Venture class Frigate (or any other small ship, but Venture was designed with mining in mind), a Mining Laser, and some basic Mining skills (of course, for high-tech mining operations, requirements can skyrocket, but so can potential profits).
Just think about inter-planetary or even inter-star system trading.
EVE Online takes the economic aspect of MMOs to a completely new level in fantasy settings, players can engage in inter-zone, or maybe inter-continental trading, but in EVE.