RUMBLETiGER
Adventurer
The Apprentice is an NPC though, and so is chosen and played by the DM, just like followers. This also requires two feats and a lot of dedication. The apprentice also doesn't accompany the Mentor on journeys unless asked as a favor, which decreases your Mentor score. It really isn't an optimized option, and the result is nothing like a Cohort. Thanks for the suggestion though.
DMGII p.179 "When the apprentice reaches 5th level, he graduates and follows the mentor as a cohort, as if she had the Leadership feat."
I do agree, this is not an optimized option, you end up with a Cohort 4 or more levels lower than yours. The Apprentice feat turns into the Mentor feat, so you really only end up requiring 1 feat. It does require a lot of dedication. But it does produce a second cohort alongside the Leadership feat.