Generic Marketplace App (Android)

I need a "Generic" Shopping App. This app should be easily modified to support various commodities. I have JAVA experience so a detailed customization guide would be preferred. Will require User friendly interaction capabilities with backend database implementation for inventory, user login information etc. I need the first build to be for an application for purchasing Cigars. I am hoping that this app can be streamlined efficiently to create additional apps for other Merchandize services and functions etc.