The domain added will have the same disk space and bandwidth of the original domain, it will have a ftp account but are not going to have a separated c-panel for that you will have to create a new hosting account.
A "resold" domain is given it's own package that contains specifications for the space and bandwidth for the that domain. Resold clients have more control over their accounts than addon domains, as they are also given cpanel.
If you are thinking on reselling hosting accounts, a reseller account is what you need
If you only want to host some of your sites you only have to know how many sites you can add to your hosting account.