If you can find a genuine person on Sythe - (Not a website, if the original owner recovers you're screwed, they won't give you money back) and get all of the information, like a picture of the ID then I would as you can generally get a level 80 for LESS then you'd have to pay for all of the expansions and the game, let alone the time you'd save.
When I say trusted I mean like a mod, someone with a huge trading record, OMM or something, not just like 10-15 vouches. If you can't find that then just buy the game yourself. Cata right now is actually on sale 50% off on Amazon.