The question usually arrives in the wrong form. How many days a week can we justify?
That is a budget question, and budget questions produce budget answers, which is how businesses end up with a senior advisor when they needed someone to run the function, or a full-time interim when what they needed was six hours of judgment a month.
The better question is about ownership: how much of the decision-making does this situation need someone else to carry? Answer that first, and the model, the days and the cost follow.
Three diagnostics
Who makes the decisions after this engagement ends?
If the answer is "we do, and we're confident about it"; you need advice, not leadership. If the answer is "we don't currently have anyone who can"; no amount of advice will close that gap.
How long does the situation need?
A defined problem with a defined end; a positioning that must be settled before a launch, a go-to-market for a new segment; is a sprint. A condition rather than a problem, such as a function that needs steering for the next year, is a standing arrangement.
What breaks if nobody owns it tomorrow?
If the honest answer is "the team keeps going, decisions just get slower," you have room for a lighter model. If it is "budgets go unspent, campaigns stall, three people wait for answers"; the function needs an owner now, and that means interim.
What each model actually buys
Advisory buys judgment without transferring ownership. Its value is precisely that the advisor has nothing to defend; no team to protect, no prior decision to justify. Its limit is equally precise: advice cannot execute, and an advisor cannot make a call that leadership is avoiding.
Fractional buys direction. Someone joins the leadership team with a real mandate for one or two days a week, sets the marketing agenda, and is accountable for progress. The constraint is arithmetic: fewer days means fewer priorities, chosen deliberately. A fractional leader given twelve priorities produces the same result as no fractional leader.
Interim buys continuity and full ownership for a defined period. It is the right answer when the seat is empty and the business cannot wait for a search. Its cost is not only financial: it is a real handover at the end, which has to be planned from the start rather than discovered in the final fortnight.
The three most common mis-picks
Buying advisory when the function needs leading. The diagnosis lands, everyone agrees, and nothing moves, because the gap was never in knowing what to do.
Buying interim when the need was judgment. Full-time presence for a part-time problem creates work to justify the days. Nobody intends this; it happens anyway.
Treating fractional as a discounted CMO. One or two days a week is not a full-time executive at 40% off. It is a deliberately narrower mandate, and it works only when the narrowing is agreed in advance.
How to get the choice right
Write the mandate before you shop for the model. One page: what this person decides, what they advise on, what they deliver, what they are accountable for, and when the arrangement ends. If that page is hard to write, the difficulty is not in the market; it is in the mandate, and hiring anyone before resolving it will be expensive.
Then choose the lightest model that carries the mandate. Ownership is not something to buy more of than you need.
The models are not a ladder to climb. They are four different answers to one question about ownership, and the right one is usually the lightest that still carries the mandate.
Marketing-led commercial growth. Strategic advisory, fractional CMO and interim marketing leadership for organizations that need direction, alignment and momentum.