Each account has an Account Owner and Account Manager. The owner is the person responsible for payments. This individual will be sent an invoice once the account is created. Payment will be via credit card. Each month, the number of account members will be reviewed and you will be billed if you go over 20 members. The manager is responsible adding new announcements, new members and all other account management and configuration.
Self-hosted applications have a monthly cost of $10 on top of your yearly account fee.