Hey @cookegrahamg
@J805 is right bubble is great for this kind of application. I have developed this kind of application for my current position. In our situation we actually go one layer deeper. We have a Distributor, Reseller and then the end customers. They all see something different.
My suggestion is build a little bit and play around with the DB. Then once you got the hang of that, really focus on how you want to manage your privacy rules as they are extremely important for an app like this.
There is also another solution if everyone of your customers (gym owners) needs a separate DB and that is to use the sub application feature. I forget what tier of bubble subscription you need to get this but check on that too.
This allows you to build an app like Zeroqode but then every time you sell it you create a sub app which is a copy of your main app but with it’s own DB. When you make changes to the main app you can push them to your sub-apps (customers).
Hope this helps! There is a lot of awesome things about bubble and it really is just learning how to apply traditional way of coding into this very flexible and fast way of developing.