There's a goldmine hiding in r/passive_income, r/EntrepreneurRideAlong, and about 28 other subreddits that most developers never bother to check. The author behind a DEV.to post published June 6 breaks down their system for mining micro-SaaS ideas from Reddit complaints—and the results are surprisingly actionable. The strategy is dead simple: instead of doomscrolling Product Hunt or burning out on Twitter discourse, open Reddit and look for threads where someone describes a workflow they hate, asks if a tool exists, and gets the reply "I wish—please tell me if you find one." That second comment is the cofounder you don't have to pay. The author calls this pattern finding "demand" and has codified it into a repeatable framework with real search volume data behind each opportunity. The first idea targets trade contractors—a market nobody wants because it sounds boring on purpose: invoice reminders for plumbers, electricians, and HVAC techs. A post on r/passive_income with 3,653 upvotes literally says "invoice reminders for plumbers" is worth $14K a month. The wedge here is surgical: connect to Stripe or QuickBooks Online, then send polite nudges at day 7, firmer emails at day 14, and a final notice template at day 30. Charge $19/month. Competition is QuickBooks (which handles this terribly) or nothing.

Solo Tradespeople Need Software Too

Field service management software assumes you have a crew. Jobber, Housecall Pro, ServiceTitan—all built for dispatching multiple technicians with GPS tracking and team scheduling. But what about the solo HVAC tech running residential calls? A Reddit post from r/EntrepreneurRideAlong asks exactly this: "Is there field service management software that doesn't assume you have a team?" The answer is no—not really. Monthly search demand sits at 8,800 queries for "field service management software" with solo and small-business modifiers. Build a stripped-down PWA handling estimates, invoices, Stripe payments, and one-screen customer history. Skip dispatching, skip crew features, skip GPS. Charge $15/month.

Compliance Tracking Nobody Wants to Own

Construction project managers are drowning in subcontractor compliance tracking. A post on r/ConstructionManagers (47 upvotes) describes the nightmare of managing COIs, licenses, lien waivers, and insurance documents that constantly expire. Monthly search volume for "COI tracking software" is 3,900 queries. The problem isn't complicated: if a subcontractor's coverage lapses and someone gets hurt on site, the general contractor eats the liability. Most firms track this in a spreadsheet nobody updates. A simple expiry tracker that uses an LLM to parse PDF documents and sends email reminders at 30/14/7 days before expiration solves exactly that. Price it at $49/month per project.

AI Chatbots for Agents Who Work Alone

A post on r/AiForSmallBusiness with 367 upvotes tells a success story: someone built a chatbot for their dad, a solo real estate agent drowning in calls and client questions. The bot qualified leads, answered listing FAQs, booked showings, and routed hot matches to a phone number. That post now has 57 paying customers. Monthly search demand for "real estate AI chatbot" is 3,500 queries. There's clearly room for a more polished version—a widget that pulls from a Notion or Google Sheet of listings, books appointments via Calendly, and SMSes the agent on high-intent matches. The sweet spot is $29/month.

Build the Librarian Into Your App

The fifth idea targets developers themselves—and it's the one with the most technical satisfaction potential. Obsidian, Notion, Logseq, Roam: all popular knowledge management tools that require you to be the librarian. A post on r/ObsidianMD with 365 upvotes nails it: "why does every second brain app feel like a second job?" Search volume for "auto-organize notes," "PKM without effort," and "second brain that just works" sits at 2,500 monthly queries. The wedge is a local-first daemon that watches your markdown vault, auto-tags new notes using embeddings, links them to existing content, and generates a weekly digest. Price it at $9/month or offer self-hosted for the technical crowd. Use Claude or a local model behind a flag—either way works.

Key Takeaways

  • The pattern across all five ideas: specific person + pain costing money/time every week + category leader built for the tier above them
  • Hunt in subreddits where people discuss their jobs, not hobbies—jobs reveal real workflow pain
  • Search patterns "is there a tool that," "what do you use for," and "I wish there was" to surface demand signals
  • Same complaint appearing in two different threads from different users confirms genuine market need
  • If the first Google result for an existing tool name is a Reddit thread, you've found undersaturation

The Bottom Line

These aren't billion-dollar ideas—and that's exactly the point. Micro-SaaS thrives on specificity: serve one underserved persona with laser-focused features and charge what you're worth. Stop building things Twitter thinks are cool. Start building things that show up in Reddit threads as "I wish there was." That's where the $2K MRR side projects live.