One of the best times to treat your home for household pests (bugs) is before you move in. The house will be empty and nothing will hinder the technician from performing a complete treatment of the home. This will help ensure your home is ready for you to move-in.
Ideally you should schedule this treatment to be right after your closing on the home. Your personal belongings may have been in storage and packed where bugs may have been. Treating your home will help prevent them from being an issue at your new home.