Hosting document

I am a lawyer. I want one web based portal to be created wherein all the clients who are desirous of sending papers can login with unique login password and upload document in case folder relating to them. They can freely add or remove documents from respective case folders. At the same time as and when me or my staff desire they will have full access to all the data and that data can be accessed by us from the same website. It is personalised Google drive.