The fastest way to waste six months of your life is to build something before you know if anyone wants to pay for it. This happens constantly in online business, usually to people who are genuinely skilled at building things — the skill is the problem, because it makes building feel productive even when it's the wrong thing to be doing.

The lean validation framework exists to interrupt that pattern. Here's how to run it properly.

Start with the most specific version of your idea you can articulate. Not "an app for fitness" — "a 14-day strength training plan delivered via SMS for people who hate gym environments." Specificity makes everything that follows easier: finding potential buyers, describing the value, measuring the response.

Spend two to three hours finding 20–50 people who match your target profile. Reddit's relevant subreddits. LinkedIn searches. Facebook groups for the niche. Twitter/X searches. Discord servers. Don't pitch yet — observe. Read the threads where they describe their problems. Note the exact language they use. The words that appear repeatedly in complaints are the words that should appear in your marketing.

Then build a one-page site. Carrd is free. Notion works. The page needs: a headline that names the problem and the outcome, three bullet points on what the thing does, and an email capture with a clear call to action. Add a question: "Would you pay £X per month for this?" Optional but valuable.

Share the page where it naturally fits. Post in the threads where people are discussing the problem. Send five cold emails to people you identified who match the profile. Post in the relevant subreddit with honest framing: "Testing this idea, looking for brutal feedback." Don't spam. Don't oversell. Ask for honest responses.

Score the response by the end of the day. Did anyone email? Did anyone say they'd pay? Did the page capture any signups? If you got five genuine responses from people who expressed real interest — not polite encouragement, but specific interest — that's enough signal to start building a minimum version. If you got silence, kill the idea and run the process again with a different problem.

The weekend you spend here is the most valuable weekend in the life of any new business idea. It costs you almost nothing. The alternative — months of building for a market that doesn't exist — costs much more.