Retainers:
Charges monthly fee for services
Pay Per Lead:
Charges based on the number of leads that are brought into the business
Pay Per Show:
Charges based on the number of shows
Pay Per Appt:
Charges based on the number of appointments generated
One-Off:
Non-retainer approach where something is charged based on a singular project
Productized:
Set it and forget it model without having much fulfillment services typically as a tool set