A reseller account is a standard business account that is able to create sub-businesses. This is useful, for example, if a small IT-support firm manages the IT infrastructure of other small firms, but does not want to run their own email servers.
FastMail charges the usual amount for business accounts in these cases. The reseller can charge their sub-business for email accounts with their own mark-up added.
There are two general modes this operates in:
In this case, you do all the management work, and don't give access to the masteruser account to the sub-business at all. They call you to do anything and you charge them at your hourly rate to do that management work, and charge them for the accounts with your own markup.
In this case, any changes bill the reseller's client credit card directly. You can give them access to the masteruser account to do their own upgrades/downgrades. This reduces your work, but you can't make any profit on the accounts. If they need help, they call you and you invoice them separately at your own hourly rate.
The first step to being a reseller is creating a business account for yourself. Then, we mark your account as a reseller account, and you can create and manage sub-businesses.
This is designed for businesses that manage the IT infrastructure of a number of other businesses from one place, and want to keep each business logically separated.
There are a number of advantages from using a reseller account, as oppossed to a single business account.