As the Reseller you are responsible for collecting payment from your clients individually. We will bill you directly for your Reseller hosting plan according to the billing cycle you selected when signing up.
If you do not have any solution set up yet, by far the best, easiest and fastest (immediate) solution seems 2CheckOut.com which integrates a shopping cart (you may not even need that for Web hosting services) with a credit card processing system in one package. They do have a one time $49 setup fee, but there are no further monthly fees (quite different from most other billing services!). You may also consider adding PayPal, it's easy to use and also allows credit cards to be accepted.