Help with FTP Users and subdomain access



I would like to set up my site so that I have access to all folders on the server, which i do.

I would also like to add about 4-5 subdomains, with 4-5 additional FTP users that can only access each of their own subdomains. And limit the amount of space each of the subdomains may use.

Any help is very appreciated.

Thank you.