When starting Checkly, the author struggled with typical SaaS billing and prorating concepts, despite understanding them intellectually. To simplify the process, they chose Stripe Billing as their subscription billing provider due to its popularity among SaaS companies. The core Stripe Billing entities include products, pricing plans, users, and subscriptions. The author implemented tiered pricing, which allows for discounts on higher volumes of usage. They also integrated Stripe Billing with their Hapi.js-based API, handling tasks such as creating customers, subscriptions, and invoices. To handle recurring payments, they listened to the `invoice.payment_succeeded` webhook from Stripe, updating account information accordingly. This setup provides a basic yet effective solution for managing billing cycles in Checkly's SaaS product.