Can I use one account Activecampaign for different businesses or is it better to use different domains?

The majority of his business is non-insurance based Plastic Surgery. Other practices under his umbrella company are insurance based (ENT, Ortho, etc...). I am going to install ActiveCampaign (potentially white-labled) for the Plastics division. My question is the other divisions want the abilities as well. Should I sell each practice it's own license or should I book it under one company and segment via lists? I'm leaning individual instances, but I don't want an ongoing nightmare of managing all of them. I'm a two man shop and don't have a ton of bandwidth.