A breathwork or coaching retreat isn't a different business model from a general yoga retreat - it's the same fundamentals (venue, pricing, list-building, marketing) applied to an audience with a specific, well-defined problem. See our guides to pricing and filling a retreat for those fundamentals - this guide covers what changes for a niche focus.
Niches built around a specific, strongly-felt problem - coaching, breathwork, life transitions, burnout - tend to convert well precisely because the audience already knows exactly what they're struggling with. Your job is narrower than a general wellness retreat: speak directly to that one problem rather than trying to appeal broadly.
Identify what you're personally qualified to lead, and contract out the rest. A coach who isn't a certified breathwork facilitator brings one in; a breathwork facilitator who isn't a chef sources one locally. Retreat guests are unusually receptive to teaching and depth during a retreat - lean into whatever specific expertise makes your version of this different from a generic wellness week.