Hi @will1971 this requires and app and using the apis, you can’t do this on shopify with only a template/theme.
Before proceeding further there should be actual valid business reasons to try and shoehorn this type of business model onto shopify.
I.e. the reason to use shopify just shouldn’t be because the client heard of it somewhere or the developer is familiar with it.
Search vendor marketplace apps on the app store and in the forums plenty of online content about this