Well, I would recommend that if you are not experienced dealing with venemous snakes that you hire someone to find the animal for you. In a house that is empty, it should make the job a little easier for a trained professional. That being said, snakes, like many animals, seek out a secure hiding spot. Dark spaces such as cupboards, closets, underneath stairs, etc. are likely locations to find him. However, finding him is only half that battle as catching and securing the snake safely is a whole other challenge. That's why I recommend hiring someone in the business of removing unwelcome wildlife from the home. See if you can find a company that also practices humane catch and release policies so the snake is not harmed.
Best of luck