Jake will be at the Aleroth graveyard and/or in his cellar until you kill him in the graveyard by the quarantine area. You can wait and level up a bit first, and kill him a couple times before getting too far away from Aleroth.
Killing him when you are at lower levels gives more experience, though. If you kill him on character level 1 (a lot of running with bow, or not so much running with potions and Meteorstrike) it will bring you up to level 3, and killing him again brings you to 4.
