Find the business and shadow the work

Two signals, neither of them technical

Volume. Something done many times a week. You already know why from the payback arithmetic: without volume nothing repays the build, however clever it is.

Irritation. Something a specific person visibly dislikes. This matters less for the economics and enormously for the delivery, because that person becomes your champion — the one who tolerates the rough first version and defends it internally when it misbehaves.

A task with volume and no irritation is a hard sell nobody will fight for. A task with irritation and no volume is a favour. You want both.

Get one owner to talk to you

Approach three local businesses. Not with a pitch — with a question: what took up your week, and where is somebody staying late?

Go in person, at a quiet hour, and say plainly what you are doing: learning, building something real, and not selling anything today. People are far more generous with that framing than with a pitch, and it happens to be true.

Shadow the task for a full day

Sit with the person who does it. Watch them do it, repeatedly, without helping and without suggesting anything.

Count the instances, time them, and write down every exception, interruption, and workaround. Pay particular attention to the things they do not mention because they are too obvious to say — those are exactly the requirements you will otherwise miss.

Observed exception rate

The share of instances during your shadow day that were not the normal case. Measured by watching, not by asking — people consistently report a lower number than they perform.

Write the discovery back to them

Describe their process back to them in one page and ask them to correct it. Every correction is a requirement you would otherwise have discovered during delivery, at ten times the cost.