It is against the Terms and Conditions to give an account away. Discreetly amongst friends with nothing other than pets (no items, NP) is borderline and I am guessing still strictly against the rules but probably not freezable over. Since that scenario could be more like a private adoption, which I *think* might be legal, but don't quote me on that. Check the T&C!
Even a close friend with NP and items is technically not allowed to gift that account to any other person. That user must self-freeze his/her account instead.
Having said that, a friendly person could legally gift all items and NP to a friend before hand, transfer their pets to that friend through the Pound, and then self-freeze the barren account and all would be kosher.
(At least I am pretty darn sure on that.) I should have just said first, please beware as I see it as simply one form of many possible scams.
And to clarify from your Subject line, yes it is freezeable to accept such. Unless this person is friendly enough to directly send you all of his/her NP and items then even transfer pets in the Pound to you, then self-freeze, it is a freezeable offence. I believe it is even in the short Terms & Conditions. Please do read that and if in doubt, ask TNT or ignore the person (or report them for harrassment if such behavior persists).