public and private app: how to manage licenses

[Indaco85]

Hello, I would like to create an app where customers can place orders by entering their data (name, surname, email, order detail) and this information can be viewed and managed by the seller. Clearly, the seller will have a private app that requires login with their email while customers can use the order app without any login (public app downloadable from the stores). Is it a workable thing? How to manage licenses? Would the seller only pay by having a private app? thank you very much