DK question

Hey, so,

I'm about to hit 55 with my mage (Lordaeron), I'll get a death knight as soon as I do it.
Now, if I trade my mage, will I be able to keep my DK? Even if I do not have another 55 on my account?

Pardon me I posted this in the wrong section before.

Come on, I know it's not hard to answer.

I Wonder The same!