All resources in the system are part of a structured hierarchy of ownership. Looking at the case of a Site, the chain of ownership would be System -> Distributor -> Reseller -> Site. The System entity is the root owner in the system, and has no owner.
Billing if resource usage is flowing upwards this chain of ownership. A site user will pay a fee to the reseller that issues the license. The reseller will pay a combined fee of all licenses it has issued to its distributor and finally the distributors will have to pay fees for all the licenses that all its resellers have issued to the system owner.
In the world of software as a service the distributor typically represents software marketplaces where resellers can sell site licenses all billed via the software marketplace provider.
A distributor manager can add and remove user-access to administer the distributor and to administer all the distributors resellers.
As a distributor administrator you are able to, either manually or via an API user, provision new resellers and manage limits on these resellers. There is no limit to the number of resellers you can add(but the system might enforce a limit to prevent e.g. API usage errors) and adding resellers will not incur any extra cost for the distributor.
The distributor can set limits on the reseller to prevent the reseller incuring limitless costs on the distributor.