Edoras wrote:
There's no benefit to the student except having it free (And that doesn't mean much)
But, training a newbie in levels, along with spending time with them and training them in other skills (And some other secret rules that we don't get to know) increase your "secret mentor points," a hidden value for each character that gives you an extra stat train at the monthly reboot if it's high enough.
When you're new to the game and don't know how to make money well (or extremely frustrating, buying armor that you cannot in any way reasonably know is even superior to yours and having everything you buy stolen) free trains end up saving a lot of money from that perspective.