First off you can add users and specify which parts of the control panel they can access. However if you are on their shared services I am pretty sure it is against the policy to do what you are stating.
The part under What's not allowed in "Unlimited"?:
Here are some specific examples of things not allowed:
* Copyrighted content to which you do not hold usage or distribution rights.
* File upload / sharing / archive / backup / mirroring / distribution sites.
* A site created primarily to drive traffic to another site.
[b]* Making your account resources available (whether for free or pay) to the general public[/b]
It would be nice if DH would allow reselling though like some of their competition and let you get 40% maybe and to be able to brand the panel with your own company information with no reference to DH. There has been suggestions for this sort of thing before but apparently not enough votes.
Now I am not sure if there would be the same requirements if you were on a dedicated server (i doubt they would care what you do with your space so long as you aren't breaking any laws).
You will have to wait to get DH's official stance on this though.