The simple answer is yes, it is possible. Not easy, not effortless, not exempt from investing a fair amount of time (perhaps too overly), but possible (although improbable for the vast majority). This is a summary of those that have ranked-up to date, needing merits in the process:


As you can see, 9 Old Era Newbies have made it to Hero, 40 Newbies (34+6) have reached Sr. Member, 111 Newbies (25+86) to Full Member, 3.357 to Member and 10.433 to Jr. Member.
Those you’re really focusing on now are the 9 Newbies that made it to Hero (nobody has had time (Activity) yet to make it to Legendary from Newbie starting from scratch under the Merit System).

As I said, feasible, yes. Effortless, no. Likely, not easy in the big picture, but those who really do try do have a shot at it.

As to the purchasing an account, I left my opinion today here: re:Whats fair price for Legendary Account?