Private Page with customer

Hi all
Iam looking for advice/help for my homepage.
I want to make a private page with my customers where both my customer and me have access to them and do the following:
– Every customers must login before have access to the page
– Share file / document / pictures.
– Add comment
– Send an invoice.

Will you please help find the right plugin or help to build this kind of pages in wordpress.

Best regards
Rafid