You're not creating an instance, you're just assigning the instance to a variable (There is a pretty large difference if you're going for correct terminology)
His way lets you check if theHouse isn't null, which is very useful if you're not sure your object actually exists (which lets you throw your own errors instead of exceptions being thrown)
One thing though - use GameObject.FindWithTag instead of gameObject.FindWithTag. It's a bit of a freaky javascript only thing where it lets you access the static function of a class through an instance. It's also a bit slower as it has to grab the gameobject first