Hi there Akiko! I believe your notion of getting 1 unit and see initial if all of them become accustomed to the Litter Robotic it’s a fantastic solution. Then, if the thing is all of them working with it, you should purchase a next just one. A single solitary unit https://automatic-litter-box65432.pages10.com/facts-about-automatic-litter-box-revealed-72484396