To charge vendors per lead in a marketplace, use CRMs like HubSpot with billing integrations, or platforms like Sharetribe for built-in lead tracking. Dedicated tools like LeadDyno and PayKickstart automate tracking and billing. For flexibility, Zapier can link lead tracking to Stripe or PayPal for invoicing. Hipages and HomeAdvisor use custom systems for scalable lead validation and automated billing, a model to consider as your marketplace grows