How I validated a product idea before spending a euro on development

TL;DR

• We almost spent €10K on a marketplace idea with zero proof anyone wanted it
• Instead we paused, surveyed parents, and got 250 responses in 2 weeks - 67% said they would use it
• That signal shaped the product - then we built it ourselves on Bubble over nearly 2 years
• Validation is not likes or opinions. It is people acting: survey answers, waitlist, calls, even tiny payments
• If you cannot find a handful of people who care, you do not have a product yet - you have a hobby

The quote that almost became a €10K mistake

It started as a simple idea: a marketplace where parents could exchange baby and kid stuff their children had outgrown. Closets full of unused things. An obvious pain. We thought - how has nobody built this here yet?

So we started asking development shops what it would cost.

The first quote was €150,000. We laughed, then panicked. More quotes followed: €80K, €30K, eventually €10,000 from a small local shop.

Even €10K felt wrong. We were first-time founders with no tech background and no proof. Dropping that money on a hunch did not sit right.

The question that changed everything

We hit pause and asked ourselves something that still shapes how we work with clients:

What if we do not build anything yet? What if we just ask people first?

So we made a survey. No ads. No budget. Just hustle through parents, friends, and Facebook groups.

In two weeks we had 250 responses. 67% said they would use a platform like that.

That was not a business yet. But it was enough signal to keep going - and enough detail to know what to build.

From interest to a real product shape

We went deeper. What people loved about second-hand groups. What they hated. What made them hesitate.

That research turned into a tight product brief: no fluff, real pain points, only the features people actually cared about.

We still had no team and no money to burn. Just time and belief. So we found Bubble and built it ourselves - evenings, weekends, stubbornness. Almost two years of testing, talking to users, and iterating.

Eventually it worked. The platform took off. Then something unexpected happened: other founders started asking if we could build their apps the same way.

One project became two. Two became five. That is how Eterna started - not as a theory about product studios, but as a path out of expensive mistakes.

What validation actually means

Validation is a real-world signal that people care enough to act. That action might be joining a waitlist, finishing a survey, booking a call, paying even €1, or sharing it with someone else.

Validation is not a polished product, social likes, or asking your mom if the idea is good.

Before you write code - or hire anyone - you want clarity on:

• Who the user is
• What problem they care about
• What messaging lands
• What they might pay for
• Whether you are even solving the right problem

Talk about their problems, not your pitch deck. Look for patterns in how they solve it today. Offer your idea as a soft "what if" and watch what they do next.

A lean validation stack you can run this week

The stack we still use:

1. Landing page - clear problem → value → CTA, with email capture or a booking link. You can start from our landing page template.
2. Short survey - 3-5 questions, optional early-access reward.
3. Targeted outreach - niche communities, DMs, emails. Track clicks, signups, replies.

If people take action, you have a thread to pull. If they ghost, good - you just saved months and a painful invoice.

Bonus: the 10-person interview method. Find where your audience already gathers. Book ten short calls. Ask what is hard, how they cope today, what sucks about that, and whether they would pay for a better way. Focus on past behavior - if they already tried to solve it, the pain is real.

A quick readiness check

1. You can state the problem in one sentence
2. You have a landing page collecting interest
3. You talked to 10+ potential users who are not just friends
4. They show real pain or hacked-together workarounds
5. You tested messaging and tracked reactions
6. You have emails, DMs, or "tell me when it is live" replies
7. Someone said they would pay - or asked to be notified at launch

Five or more: you are ready to build lean. Two to four: keep testing. Zero to one: go back to the problem before you open the calculator or book a build.

If you want help getting to signal

This is still how we start many engagements - especially Application builds. Prove demand first, then ship the lightest product that can earn learning.

Use the template, run the interviews, or book a free 15-minute strategy call and we will map the lightest next step - Blueprint, landing validation, or a tighter scope.