Very little. ATRIUM builds a social network or "super app" from a single AI prompt, rather than through traditional software development.
What you need before you start: A UIID to sign in with, and a clear idea of who the community is for. That is genuinely it — there is no hosting or infrastructure to set up.
What you can decide later: Your colour scheme, logo and favicon (Design → Change Site Design), where your data is stored, which payment gateway you use, and which providers power video, audio and SMS. None of it has to be settled before you launch.
What it costs: A flat infrastructure fee of one cent (US$0.01) per user per month. You keep 100% of your revenue — no platform cut on subscriptions, paywalled content or your own ad network.
Where to start: web4.community.
A realistic expectation: Launching is quick. Growing a community is not. The platform removes the technical barrier, not the community-building work.