As a beginner, you really don't need membership, so it's free for quite some time, but once you finish all those Free quests, and have the best gear that the free edition offers, then you will get insanely bored unless you purchase members which is like 6 or 7 dollars a month like Shadowesh said.
If you have membership from the get go, getting money is a lot easier aswell as there is much more places to explore and a lot of other quests to do. But like I said, its a free game, but paying unlocks a lot of content that will help you and make the game a lot more fun.
Sorry for wall of text, but if you plan on playing, I highly recommend you get a membership.