Build a Website with a backend user management system (users and sub-users)

A. SCOPE - Website for users to manage their expenses: - User starts with expense = 0 - User can login and add an expense - User can see his accumulated expenses so far - IMPORTANT - parent-child relationship between users of same account is required: 1) "parent" user creates new account 2) "parent" user can create additional "parent" users within his account 3) Any "parent" user can create "child" users within his account 4) Different permissions levels for "parent" vs. "child" (system level, not configurable by users): a. "parent" users can: - Login/logout/change password/reset password - Create additional parent users - Create child users - Register new expense per child user + attach comment & date per expense - View total accumulated expenses - per child - View expense history (previous expense entries with details, in a table format) - per child b. "child" users can: - Login/logout/change password/reset password - View total accumulated expenses for their own user - View expense history (previous expense entries with details, in a table format) B. NOTES: 1) Website should be responsive (view on tablet/mobile). 2) Future proof: architecture that can be expanded in the future (e.g. notification system, scheduled events etc.). 3) Maintainable: website including backend should be transferred to owner for future maintenance and possible further development. 4) Would like to get proposal with and without graphic design (in case work delivered without graphic design should be easily possible to combine CSS template of my own)