Online Consultations App (Web/iOS/Android)

The requirement is to develop an online consultations platform (web/iOS/Android) that provide paid consultations and utilizes both asynchronous (text/audio) and synchronous (VoIP) communications. No specific technology stack determined.
The work must:
primarily utilize pre-existing tried and tested components (e.g. scripts/templates etc)
User access and roles management
Integration with payment gateway and other 3rd party APIs
User profile and historical interactions
implement the required business procedures/logic
maintain users data encrypted in Db.

iOS/Android applications may be developed later but the web app must be structured such that it accommodate the iOS/Android apps. For iOS/Android, Flutter/Ionic are preferred.

Detailed SoR is available and will be shared in due course.

For an application to be considered, the developer must provide a concept document highlighting
- tech stack and justification
- Overall structure/architecture (identifying all scripts/components/templated that will be utilized)
- Activities and deliverables over a timeline.