"How long until SEO works?" is a fair question that usually gets a useless answer. So here's an honest one, with actual ranges instead of "it depends".
Months 1–3: foundation
Early on, you're fixing and building, not ranking. Technical clean-up, getting your core pages right, publishing your first genuinely useful content. You may see small movements, but this is groundwork, not payoff.
Months 3–6: early signal
This is usually when long-tail and local searches start to land. Specific, lower-competition terms, "the exact thing you do, in the place you do it", begin sending real enquiries. It won't be a flood, but it's proof the engine is turning.
Months 6–12: compounding
This is where SEO earns its reputation. The content you published months ago starts ranking, your authority builds, and leads arrive without you paying per click. The work you did early keeps paying off long after.
What changes the timeline
Competition in your space, how often you publish, the state of your site when you start, and consistency. The single biggest variable is whether you keep going, most businesses that "tried SEO and it didn't work" simply stopped at month three.
SEO is slow to start and hard to stop, which is exactly what makes it worth doing.