I have a side habit. When I run out of ideas for what to build next, I do not open Twitter or Product Hunt. I open Reddit.
There are about thirty subs where the same complaint comes up every week. Someone describes a workflow they hate, asks if a tool exists, and a commenter says "I wish, please tell me if you find one." That second comment is the cofounder you do not need to pay.
Here are 5 I pulled from threads in the last few months. Each one has a real Reddit post behind it, real search volume on the keyword someone would type into Google, and a wedge small enough to build over a weekend.
None of these are billion-dollar ideas. All of them could be a $2k MRR side project if you actually shipped.
1. Invoice reminders for trade contractors
"i know the title sounds made up. invoice reminders for plumbers. $14K a month. but that's exactly why it works. nobody is competing for this."
r/passive_income, 3,653 upvotes
Search demand: 7,200 monthly searches for "invoice reminder software" and adjacent terms.
Why it works: plumbers, electricians, and HVAC techs send invoices and then forget about them. Their customers also forget. Nobody wants to be the awkward one chasing money. A scheduled email or SMS sequence converts ghosted invoices into paid ones. The buyer is one tradesperson, the value is measured in actual dollars recovered, and the competition is QuickBooks (terrible at this) or nothing.
Wedge: a single Stripe-or-QBO connector that sends a polite nudge at day 7, a firmer one at day 14, and a "final notice" template at day 30. Charge $19 a month.
2. Field service software for solo tradespeople
"Is there field service management software that doesn't assume you have a team? I run residential HVAC solo, sometimes one helper when it gets busy. Everything I've tried is built for dispatching crews."
Search demand: 8,800 monthly searches for "field service management software" with solo and small-business modifiers.
Why it works: Jobber, Housecall Pro, ServiceTitan all assume you have at least 3 people. Solo HVAC, plumbing, and handyman operators just want estimates, invoices, payments, and a customer history. The category leaders all charge $50 to $200 a month for features the solo operator never opens.
Wedge: stripped-down PWA with estimates, invoices, Stripe payments, and a one-screen customer log. $15 a month. Skip dispatching, skip crew, skip GPS.
3. Subcontractor insurance and compliance tracking
"New PM here. Am I crazy, or is tracking sub insurance a complete nightmare? My boss has me managing all the subcontractor compliance (COIs, licenses, lien waivers) and it's a constantly expiring mess."
r/ConstructionManagers, 47 upvotes
Search demand: 3,900 monthly searches for "COI tracking software" and "subcontractor compliance."
Why it works: every general contractor needs to verify that every subcontractor has current insurance, licenses, and lien waivers. If a sub's coverage lapses and they get hurt on site, the GC is liable. Most firms track this in a spreadsheet that nobody updates. A simple expiry tracker with email alerts to the sub and the PM is genuinely high-value.
Wedge: upload a PDF, parse the expiry date with an LLM, send email reminders 30/14/7 days out to both parties. $49 a month per project.
4. AI lead chatbot for solo real estate agents
"A few months ago, I built a chatbot for my dad who's a real estate agent. He was always juggling calls, emails, and client questions. Now 57 people are paying me for it."
r/AiForSmallBusiness, 367 upvotes
Search demand: 3,500 monthly searches for "real estate AI chatbot" and related queries.
Why it works: solo agents lose deals because they cannot reply at 9 pm. An AI that qualifies leads, books showings, answers FAQs about listings, and routes hot leads to a phone is genuinely useful. The Reddit thread above is itself proof: the OP is currently making money from exactly this. There is room for a more polished version.
Wedge: embeddable chat widget that pulls from a Notion or Google Sheet of listings, books to Calendly, and SMSes the agent on a hot match. $29 a month.
5. A second brain that maintains itself
"Or, phrased differently, why does every second brain app feel like a second job? All of the tools that actually resemble a 'second brain' require an enormous amount of upkeep."
Search demand: 2,500 monthly searches for variations of "auto-organize notes," "PKM without effort," and "second brain that just works."
Why it works: Obsidian, Notion, Logseq, Roam. All of them require you to be the librarian. The market for "the librarian is the app" is wide open and devs are loud about wanting it. The audience is technical, which means they will pay for a tool that respects their files, and they will tell their friends.
Wedge: a local-first daemon that watches your markdown vault, auto-tags new notes, links them to existing ones using embeddings, and writes a weekly digest. $9 a month or self-hosted. Use Claude or a local model behind a flag.
The pattern
If you read those five back to back, you notice a shape. Each one is:
- A specific person (solo HVAC tech, construction PM, real estate agent) with a workflow they describe in their own words.
- A pain that costs them money or time every single week.
- A category that already has a leader, but the leader is built for the tier above them.
The framework is dumb and works:
- Find a sub where people talk about their job (not their hobbies).
- Search for "is there a tool that," "what do you use for," and "I wish there was a."
- When you see the same complaint in two different threads from two different people, you have demand.
- Search the existing tool name on Google. If the first result is a Reddit thread, the market is undersaturated.
A shortcut
I got tired of doing this manually so I built Business Ideas DB. It scans roughly thirty indie subreddits every day, scores posts for genuine pain versus venting, attaches real keyword volume from DataForSEO, and surfaces the ones that look like buyer demand. The signals are the actual Reddit posts, not AI fluff.
If you would rather have the list, that is what it is for. If you would rather hunt yourself, the framework above is what I do when I hunt.
Either way, go build something. The world has enough Twitter threads about building.
Top comments (0)