---
title: Test demand with ads before building the app (pre-sell)
slug: presell-demand-test-before-building
summary: Yuliya Lennox's rule — before vibe-coding an app, run marketing that sells a PDF, concept or promise (refunding if needed) to learn audience size, acquisition cost and willingness to pay; plus why founders must do early marketing themselves.
domain: mobile-apps
tags: [user-acquisition, validation, paid-social, founders]
related: [meta-ads-readiness-checklist, app-break-even-cpi-and-revenue-per-install, founder-led-virality-before-ugc, app-mvp-single-problem-scope]
sources: [yt:jzlPf100vy4]
updated: 2026-10-24
---

# Test demand with ads before building

## TL;DR (Yuliya Lennox, July 2026)
- **Start with marketing, not code**: sell a PDF, an idea or a pre-order — and refund if there's no product yet.[^1]
- What you learn: is the audience big enough, how expensive is a new user, can monetisation ever cover it?[^2]
- Her example: an aquarium-keepers app idea — marketing would show a small, expensive-to-reach audience; fine for a $20k/month side income, not for a VC-scale LTV:CAC.[^2][^3]
- Don't trust family and friends' encouragement as validation.[^4]
- **Founders should feel marketing first-hand** — sit in acquisition meetings, think up early creatives. Eva Learn English (once #2 language app after Duolingo) had a founder in every marketing meeting.[^5][^6]

## Details
**Bootstrapping on paid is hard.** David Barnard's math in the same conversation: reaching ~$20k/month profit on traditional performance marketing might take $100–200k/month in spend and a full-time year where most revenue is reinvested; subscriptions only start cash-flowing in year two if retention holds.[^7][^8]

**Practical version (derived):** landing page or web quiz describing the outcome → small Meta budget against your target audience → measure CTR, cost per lead/checkout and actual pre-purchases → refund or deliver a simple version (PDF/plan).

## Disagreements / caveats
- Collecting money for a non-existent product needs clear disclosure and prompt refunds to stay within consumer law and platform policies.
- Niche apps can still work via UGC, partnerships or ASO rather than paid (David's pushback on the aquarium example).[^9]

## See also
- [[meta-ads-readiness-checklist]], [[app-break-even-cpi-and-revenue-per-install]]
- [[app-mvp-single-problem-scope]]
- [[people/yuliya-lennox]]

[^1]: yt:jzlPf100vy4 @ 09:06 — Yuliya Lennox
[^2]: yt:jzlPf100vy4 @ 09:55 — Yuliya Lennox
[^3]: yt:jzlPf100vy4 @ 11:36 — Yuliya Lennox
[^4]: yt:jzlPf100vy4 @ 13:09 — Yuliya Lennox
[^5]: yt:jzlPf100vy4 @ 13:58 — Yuliya Lennox
[^6]: yt:jzlPf100vy4 @ 15:11 — Yuliya Lennox
[^7]: yt:jzlPf100vy4 @ 13:09 — David Barnard
[^8]: yt:jzlPf100vy4 @ 13:58 — David Barnard
[^9]: yt:jzlPf100vy4 @ 09:55 — David Barnard