Building a SaaS typically means burning cash on API calls before you see a dollar. Not anymore. OpenRouter — the unified API for 200+ LLMs — offers free tiers on models like Mistral 7B, Llama 3.1 8B, and even GPT-4o-mini occasionally. Here’s how to weaponize them. 1. Prototype without credit cards Sign up at openrouter.ai and grab your API key. No top-up required. Start with meta-llama/llama-3.1-8b-instruct:free . It’s shockingly capable for chat, content generation, or basic RAG. 2. Build a ‘good enough’ AI feature Need a landing page generator? Email composer? Customer support bot? The free models handle 90% of common tasks. Use low temperature for deterministic outputs, add a fallback to a paid model if needed. 3. Scale with fallbacks Once you have paying users, switch to paid models like GPT-4o or Claude 3.5. OpenRouter lets you define models: ["free-model", "paid-model"] — so your free tier handles load until revenue kicks in. 4.…