How it works in general is that you receive a certain amount of space. This space is yours to sell per month at whatever cost you like. And you can offer as many accounts as you like, (Your space permitting ofcourse.)
Then your cost to keep the account per month is $20.00/USD.
This is what you pay to the hosting company.
With these accounts you also have the benifit of not only earning money from your clients that you will sign up, but you can literally get free reselling by refering qualified clients.
If you have any other questions, do not hesitate to ask. I will also update the website to clearly reflect this fact.