It could happen, I suppose. The problem (well, one of the problems) is that the giver could yoink the account back at any time. Not such a big deal if you got it free, I suppose.
Other than being against the EULA, you also have to take into account that you don't know what the characters' reputations are like; also, there's a decent chance that you won't have a clue about how to play that character - particularly at higher levels.
I wouldn't flame him for it, but I'd prefer to get my own account and start fresh, personally. The only reason I'd consider getting a second hand account these days is to PL a character up to a level where she could find a group, and only then if it were a class I'd played before.
____________________________
In a time of universal deceit, telling the truth is a revolutionary act.