Customizable Client Portal Development

I am looking for a developer to create a customizable client portal system for my business. The portal will be used for multiple purposes including tech support, sales, customer communication, and client management.

Main features I am looking for include:

* Private client login for each customer
* Individual client portals/dashboard
* Booking or appointment scheduling pages
* Client messaging system (chat and/or email integration)
* Calendar integration
* File and photo uploads
* Invoice viewing and document storage
* Secure document sharing
* Customer support integration using Zoho (embedded Zoho support form/ticket system)
* Admin controls that allow me to manage and customize each client’s portal
* Ability to modify portal features and layout based on each client’s specific needs
* Mobile-friendly design
* Clean and professional UI

I need the ability to:

* Upload documents, photos, and resources for clients
* Organize information per client
* Manage access permissions
* Add or remove features depending on the services I provide to that client

This portal will be used across different industries and workflows, so flexibility and scalability are very important. I am open to recommendations for the best platform, framework, or tech stack to build this on.

Please include:

* Examples of similar portals or dashboards you have built
* Suggested technologies/platforms
* Estimated timeline
* Estimated cost
* Whether ongoing support/maintenance is available