The most expensive mistake in bootstrapping is building something nobody will pay for. It is expensive not only in wasted development time but in the psychological cost of discovering the problem after the product exists and the launch has been announced. The antidote is to sell before you build.

This is not a new idea. But it remains underused because it requires founders to have uncomfortable conversations with strangers at a moment when they have very little to show. Showing a deck or a Figma mockup and asking someone to commit money to it feels premature. It is also exactly the right signal to collect.