I built 11 payment-enabled AI APIs in 48 hours — here's exactly how

Last weekend I had $0 in online income. By Sunday evening I had 11 APIs running on the internet, each one charging other AI agents $0.005 USDC per call automatically. No employees. No store. No prior coding experience. Here's exactly what I built and how. The Problem I Was Solving I'm building a Polymarket trading agent. It needed: Real-time crypto sentiment data Macro economic signals Whale wallet movement data Fear & greed composite index I couldn't find a single clean, cheap API that did all of this well. So I built it myself. Then I built 10 more. The Tech Stack Every agent uses the same stack: Python + Flask — dead simple API framework Railway.app — $5/month hosting, deploys from GitHub in minutes NewsAPI — free tier for headline data x402 protocol — Coinbase's open payment standard for micropayments Base chain — Coinbase's L2, gas fees under $0.01 Total cost to build: $0 Monthly infrastructure: $50 for all 11 agents Net ROI if they reach target traffic: 330x The x402 Protocol — T