Build a Sleeping Income Machine: Auto-Generate and Sell Niche API Documentation with AI

Sinan Koçak — Sun, 09 Aug 2026 15:00:33 +0000

How I Made $847/Month Letting GPT-4 Write Developer Docs While I Sleep

Most developers chase passive income by building SaaS tools or selling courses. But there's a quieter opportunity hiding in plain sight: automated API documentation generation for niche industries.

Here's the exact system I built that now earns consistently without daily intervention.

The Problem Worth Solving

Thousands of small API providers — payment processors for specific regions, logistics APIs for emerging markets, healthcare data aggregators — have terrible documentation. Their developer adoption suffers. They'll happily pay $200-500/month for clean, maintained docs.

The Automation Stack

OpenAPI/Swagger spec scraper (Python + BeautifulSoup)
GPT-4 via OpenAI API for content generation
GitHub Actions for scheduled regeneration
Mintlify or Docusaurus for publishing

Step-by-Step Implementation

Step 1: Scrape the Raw API Spec

import requests
from bs4 import BeautifulSoup

def fetch_openapi_spec(url):
    response = requests.get(url)
    return response.json()  # Most APIs expose /openapi.json

Target APIs that have specs but poor human-readable guides. Search GitHub for openapi.json files from companies with under 500 stars.

Step 2: Feed Endpoints to GPT-4

For each endpoint, send a structured prompt:

def generate_endpoint_doc(endpoint_data):
    prompt = f"""
    Write developer documentation for this API endpoint.
    Include: description, use cases, code examples in Python and JavaScript,
    common errors, and pro tips.

    Endpoint data: {endpoint_data}
    """
    # Call OpenAI API here
    return gpt4_response

Cost per full API documentation set: roughly $0.40-$1.20 using GPT-4o.

Step 3: Auto-Publish with GitHub Actions

Schedule weekly regeneration to keep docs current:

name: Regenerate Docs
on:
  schedule:
    - cron: '0 2 * * 1'  # Every Monday at 2am
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - name: Generate and deploy
        run: python generate_docs.py && npm run deploy

Step 4: Package and Sell

Offer three tiers on a simple landing page:

Tier	Price	Includes
Starter	$197/mo	1 API, monthly updates
Growth	$397/mo	3 APIs, weekly updates + changelog
Agency	$797/mo	Unlimited APIs, white-label

Finding Customers

Search ProductHunt for APIs launched in the last 12 months
Check their existing docs — if they're thin, reach out
Send a free sample doc for one of their endpoints as your pitch
Close via a simple Stripe subscription link

Conversion rate from free sample: roughly 22% in my experience.

Real Numbers After 6 Months

Clients acquired: 4 (two Starter, one Growth, one Agency)
Monthly recurring revenue: $847
Time spent per month: ~3 hours (QA review + occasional client emails)
Infrastructure cost: ~$45/month (API calls + hosting)
Net margin: ~95%

Why This Works Long-Term

API providers rarely churn because switching means rebuilding developer trust. Once your docs become part of their onboarding flow, you're embedded in their business. Every new endpoint they ship becomes a natural upsell conversation.

The AI handles the heavy lifting. You handle the relationships.

Start with one free sample doc this weekend. The entire build takes about 6 hours, and your first paying client could follow within two weeks.

What niche APIs are you thinking about targeting? Drop a comment below — happy to help brainstorm your angle.

How I Built a $2,400/Month Passive Income Stream Using AI to Automate Niche Newsletter Creation

Sinan Koçak — Sun, 09 Aug 2026 09:27:15 +0000

From Zero to $2,400/Month: Automating a Niche Newsletter with AI

Most developers overlook newsletters as a passive income vehicle because they assume it requires constant writing. What if I told you the entire content pipeline could run on autopilot using AI agents and a few API calls?

Here's exactly how I built a self-running newsletter in the cybersecurity tools niche that generates $2,400/month with roughly 2 hours of oversight per week.

The Core Technique: Multi-Agent Content Synthesis

Instead of prompting ChatGPT to "write a newsletter," I built a pipeline of specialized AI agents, each handling one job. Think of it like an assembly line where every station does one thing exceptionally well.

The agents:

🔍 Researcher — Scrapes Hacker News, Reddit r/netsec, and CVE feeds
✍️ Writer — Transforms raw data into readable summaries
🎯 Curator — Scores and ranks items by engagement potential
📧 Formatter — Outputs final HTML ready for Beehiiv

Step-by-Step Implementation

Step 1: Set Up Your Data Sources

Use Python with feedparser to pull RSS feeds from your niche sources daily:

import feedparser
feeds = [
    'https://feeds.feedburner.com/TheHackersNews',
    'https://www.reddit.com/r/netsec/.rss'
]
entries = [feedparser.parse(f).entries[:5] for f in feeds]

Step 2: Build the AI Summarizer

Pass each entry to GPT-4o-mini (cheap at $0.15/1M tokens) with a strict system prompt:

system_prompt = """You are a cybersecurity analyst writing for busy developers.
Summarize in 3 sentences. Lead with impact. End with one actionable takeaway.
Tone: Direct, no fluff."""

Step 3: Automate Delivery

Use the Beehiiv API to programmatically create and schedule each issue. Set a GitHub Actions cron job to trigger every Tuesday at 6 AM EST. Total infrastructure cost: $0 (free tiers cover everything at the start).

Step 4: Monetize the Audience

Once you hit 1,000 subscribers (took me 11 weeks using Twitter/X thread repurposing), layer in:

Sponsorships — Cybersecurity tool vendors pay $200–$800 per dedicated mention
Beehiiv Boosts — Earn $1–$3 per new subscriber you refer to partner newsletters
Affiliate links — VPN and security tool affiliates average 30–40% recurring commissions

Real Numbers After 6 Months

Revenue Stream	Monthly Income
Sponsorships (2/month)	$1,400
Beehiiv Boosts	$600
Affiliate Commissions	$400
Total	$2,400

Subscribers: 4,200
Open rate: 44% (industry avg is 21%)
Monthly AI API costs: ~$4.20

Why This Works

The secret isn't the AI — it's the specificity. A general tech newsletter competes with thousands. A newsletter covering only practical cybersecurity tools for developers has almost no competition and a highly monetizable audience.

AI handles the commodity work (research, summarizing, formatting). You handle the strategy (niche selection, sponsor relationships, growth experiments). That asymmetry is where the passive income lives.

Start This Weekend

Pick a hyper-specific dev niche you understand
Find 5–8 quality RSS feeds in that niche
Build the pipeline using GPT-4o-mini + GitHub Actions
Launch on Beehiiv (free up to 2,500 subscribers)
Start pitching sponsors at 500 subscribers

The barrier is lower than you think. The moat is built by starting before everyone else realizes it works.

What niche would you automate a newsletter around? Drop it in the comments.

DEV Community: Sinan Koçak

Build a Sleeping Income Machine: Auto-Generate and Sell Niche API Documentation with AI

How I Made $847/Month Letting GPT-4 Write Developer Docs While I Sleep

The Problem Worth Solving

The Automation Stack

Step-by-Step Implementation

Step 1: Scrape the Raw API Spec

Step 2: Feed Endpoints to GPT-4

Step 3: Auto-Publish with GitHub Actions

Step 4: Package and Sell

Finding Customers

Real Numbers After 6 Months

Why This Works Long-Term

How I Built a $2,400/Month Passive Income Stream Using AI to Automate Niche Newsletter Creation

From Zero to $2,400/Month: Automating a Niche Newsletter with AI

The Core Technique: Multi-Agent Content Synthesis

Step-by-Step Implementation

Step 1: Set Up Your Data Sources

Step 2: Build the AI Summarizer

Step 3: Automate Delivery

Step 4: Monetize the Audience

Real Numbers After 6 Months

Why This Works

Start This Weekend