A few years ago I wanted to make a niche marketplace to sell/trade tabletop miniatures. Instead of actually building the thing, I made a few mockup interfaces pages, and then just made a responsive HTML page. None of the buttons actually worked. I then put a modal that said "launching soon, sign up now for news and a special bonus on launch".

I spent $100 on ads on reddit and targeted forums with the goal to get 100 emails. If I got 100 emails, I would actually try and build the thing.

I got ~57.

You can market very far without anything that works. This is the "growth hack/MVP" mindset. I saved myself weeks of programming which would have been fun, but arguably a waste to building that specific business.

How did you determine if that 100 email cutoff you set is reasonable or not? Honest question.

I knew it was a small niche market, and I set it as really a "reasonable" goal.

"If 100 people in 30 days are interested with this ad spend, then I'll reach out engage them and build the thing."

Depending on your app/market, you can change that number accordingly, but I think 100 is just a great "feel good" number thats hard enough to hit as evidenced by my test.

> how is my audience supposed to know what I have to offer until they have it in front of them?

This is, in an essence, sales. One need not be dishonest. Talking about upcoming products is fine. Collecting early sign-ups and for manufactured products, taking deposits, is ethical.

As one of the points in the article: listen, don't talk!

Listen to problems people have now before you build so you know what to build. Then you can easily explain your product in terms of their problems.