How can I add a subscription model to my static website (Netlify, HTML/CSS/JS) without backend or database?

I've built a simple website using AI-generated HTML, CSS, and JavaScript on Netlify's free hosting. It shares my handwritten notes and college course content to help students ace exams by focusing on key topics. Now it's gaining traction, and I want to monetize with a subscription model—users log in, pay once (or subscribe), and unlock protected content.​

The challenge: No backend server, database, or domain management system. Can Netlify's free plan handle logins, payments, user data storage, and content protection (hide notes/PDFs behind auth)? Hosting platforms like Netlify offer serverless functions and Identity for this without full backends. I need code snippets or steps to integrate Stripe (or Razorpay for India), store basic user status (e.g., via Netlify Identity or external like Firebase Auth), and show content only post-payment—pure frontend with minimal serverless.​

Has anyone done this on static sites? Tutorials for Netlify + Stripe paywall? Indian-friendly gateways? Tools like Memberstack or Lemon Squeezy for no-code? Free tier limits okay for starters?