While technically it's not a multisite, it behaves so - each site it serves looks like an individual site even though there is only one code base. They all share some common content like news, products, services, etc. However, content is configurable by salon admins. They can add news or hide some common items, upload products or galleries, and so on.
When salon admins log in they can see and manage their own content only. It was challenging setting up roles properly but ProcessWire (and especially the Admin Restrict Branch module) was a perfect fit. It would require much more work and development time with another tool.
Page layouts are the same for all but there are many color schemes to choose from. These were often custom-made ones to match a new member salon's primary color.
We have more than twenty members so far and they are very happy having a professional-looking and fast website that is easy to manage.