PeopleSoft AR Billing

We would like to use our PeopleSoft AR billing to start creating bills for a different system that is currently creating bills. In order to know if we can switch over, they need to know if and how we can setup certain things. They have some companies who they bill annually, some are monthly and some are a one time bill. Where do we go in PeopleSoft and how do we setup these schedules and how do we tie it to the billing? Now the next question is just a what if scenario that only happens once in a while.