There's no single number, because 'build a business automation system' can mean different things. It might be a marketing engine that researches, writes, translates and publishes content and runs cold outreach with follow-up on its own. It might be an operations system that handles reporting, monitoring, lead handling, scheduling or customer messaging on a schedule, and only interrupts a person when a decision genuinely needs one. Or it might be a full production web app with payments, logins, a database, multiple languages and multiple tenants. Scope decides the timeline, not the other way round.
In practice the order of work sets the pace. We map the manual process first and say plainly what a system can and cannot take over, because that changes what actually gets built. A narrow system, one scheduled job wired into tools a business already uses, can go from mapping to running in a matter of weeks. A full application with authentication, payments and multi-tenant data takes longer, usually stretching into months, since more pieces have to work correctly together before it can be trusted to run without someone watching it.
Two things affect the calendar beyond scope. We take a small number of engagements at a time, so a start date depends on our capacity as much as on the build itself. And a system isn't done when it ships: we operate what we build, so there's a stretch after launch where it runs against real data while we watch for edge cases before it's left fully unattended. That operating phase is real work, not a formality. We run this way ourselves, more than 110 scheduled jobs around the clock across over 40 live integrations, 88 systems in production, content going out in 7 languages, so the timeline we give reflects what it actually takes to keep something like this running, not just what it takes to get a demo working.