Revenge of the Witch question

Hi y'all! A friend of mine is looking for a series/book that he read when he was younger. He doesn't remember much of it, but he believes the main character was a boy in high school who needed a job. He ended up finding a job to work as a house caretaker for a wealthy man in town. That man tells him to not do something in specific, but my friend doesn't remember what it was. The boy doesn't listen and ends up causing the undead to come alive in town. And at the end of the book, the very man he's working for, yawns and he realizes that man has fangs in his mouth. I'd appreciate if anyone could help!! He said it was similar to The Last Apprentice series, but it was set in more modern day time! He read it back in 2011-2013!