The point isn't to finish selling before you build, the point is to start selling -- do market research -- before you build.
You use the term "investment" -- do you invest in stock market / bitcoin / real estate by buying whatever looks cool, and chalking up your losses to the learning process, or do you research your choices and look for ROI opportunities??
I agree that your interpretation is right, but "start selling" is an extremely ambiguous phrase here. After all, "a sale" is most often understood to be a finalized sale; "to sell" is most often understood to be completed transaction.
Yes, the idea here is, "understand who you're marketing to and what they're looking for before you start building," and the phrasing used is what it is because that's catchier, but it's still not particularly concrete phrasing.
> "to sell" is most often understood to be completed transaction.
That is certainly the understanding of laymen. However, if you talk to people who work in sales, and look at their "pipelines" for creating sales leads, followup, closing, and whatever else they do, you get the sense that "selling" is actually an extensive, multi-part process. At least I think that's the view most sales professionals would have.
I think your comment about investing in other assests only further agrees with my point. Selling before you build is like investing in an asset without due diligence.
You use the term "investment" -- do you invest in stock market / bitcoin / real estate by buying whatever looks cool, and chalking up your losses to the learning process, or do you research your choices and look for ROI opportunities??