want to become Legendary 
Then... Put in the actual effort and trust to get there. Buying accounts is like buying someone else's life. Unless you are out to scam, why do you need Legendary? Seriously? Well, since Legendary ranked accounts sometimes get paid more than Hero accounts in signature campaigns, that is one reason. But it's pretty marginal, so I'm guessing anyone buying a Legendary account is doing it for more than just signature campaigns. That's not to say it automatically means scamming, though.