Under SharePoint you can Monitor the Space Allocation Usage per Site. This is a summary Page, which shows up how mutch space a Folder, is using. Please see attachements in gif. The default is, that this summary page is shown only per site and not per a site collection.
so what is a site collection: A site collection under SharePoint is a Top Level Site which as many other Subsites.
We would now like to have for the Administrator a "WebPart" or a "Tool" or a ".aspx Page" which collects this Space Allocation Summary Information for all sites under a site collection in a "single report".
It can be a WebPart for the Administrator, It can be a Tool, A Script or just a .aspx File.
You must know SharePoint and Windows SharePoint Services.
You find the Space Allocation Summary Page in SharePoint WSS under:
Site SettingsSite Collection AdministrationView storage space allocation
Please make only serious offers.