Hi Akiko! I think your concept of having one unit and see to start with if they all become accustomed to the Litter Robot it’s a superb approach. Then, if the thing is them all applying it, you can purchase a next a single. 1 one unit received’t be plenty https://pet-store-online98764.blogars.com/35776757/the-greatest-guide-to-robotic-pet-cleaning