The agency model: a team of specialists (strategist, account manager, designers, copywriters, ads buyer) does the work, with an account manager as the client interface. The client pays for the specialist labour AND the management overhead, typically 30 to 50 percent of the retainer.
The fractional-CMO model: a senior part-time strategist hands the client a plan and leaves execution to others (in-house team, agencies, freelancers). Works for venture-backed startups with marketing teams to direct. Fails for solo experts who have nobody to hand the plan to.
The operator model: one practitioner (or a tight team of two to three) does the strategy and the execution, on the client's accounts, with the client in the loop. No management layer. No production team hidden behind a project lead. The person who designs the system is the person who runs it.
Why the operator model fits a solo expert. The economics work because there is no management overhead to fund. The accountability is clear because there is one person responsible for the whole engagement. The dependency is bounded because the operator's intent is to train the client to run the system solo by month 12 (see Done-with-you).
The operator model is rare because it is structurally harder to scale. An operator can serve only a handful of clients at once. IGP caps intake at two new clients per month for exactly this reason. Scarcity is not marketing; it is what makes the operator model honest.