Hiring a digital ad agency is unusual among marketing purchases because the agency spends your money as well as charging you a fee. That makes the fee model a genuine question of incentives rather than a billing detail, and it makes ownership of the accounts a question of leverage rather than administration. Most disappointing engagements fail on one of three things: an incentive that rewarded spending, a senior team that disappeared after the pitch, or a measurement approach that could never distinguish sales the ads created from sales that would have happened anyway. This page addresses all three before it addresses tactics.
Fee models and the incentives they create
Percentage of spend is the oldest model and the most obviously conflicted: the agency earns more by spending more, and nobody in that arrangement is paid to tell you to reduce budget. It survives because it scales administratively and because clients like the simplicity. Flat monthly fees remove that conflict and introduce another, since a fixed fee rewards minimal effort once the account is stable. Hybrid models with a base fee plus a small variable component, or performance components tied to a metric you both trust, tend to work best. Whatever the model, ask two things: what the fee is as an absolute number, and what happens to it when spend falls. An agency whose fee is unaffected by a budget cut is one you can trust to recommend a cut when the numbers stop working.
Ownership and access, settled before the start
You should own the ad accounts, the billing relationship, the conversion tracking, the audiences and the creative files, with the agency holding access rather than title. This is not distrust, it is continuity: agencies change, and a business that has to rebuild its conversion history and audiences because the accounts sat inside a partner's structure loses months of learning that money cannot buy back. Get it in writing, including what happens on termination and how long the handover takes. Ask also who has publishing access and whether any work is subcontracted, because in this industry subcontracting is common and rarely volunteered. The name on the invoice is not always the hand on the account, and you are entitled to know which junior is making changes to a budget you are funding.
Measuring whether the ads did anything
Platform dashboards report conversions they can claim, which is not the same as revenue that would not have existed otherwise. The honest instruments are incrementality tests: geographic holdouts, a clean and deliberate pause on a channel, or a properly designed conversion lift study. A serious agency will propose one before you ask and will accept that some of what it reports is not incremental. A weaker one will insist that last-click attribution is sufficient and will treat any test as an attack. Meanwhile, keep one blended figure of your own: total revenue divided by total marketing spend, tracked over time. It hides channel detail but it cannot be re-cut, and when it diverges from the dashboard the dashboard is usually the one that is wrong. Buyers focused specifically on search auctions should apply the same tests when hiring a Google ad agency, where platform-reported returns are especially flattering.
What to ask in the pitch
Ask to see an account they manage, screen shared, rather than a case study slide. Ask what they would turn off in your account in the first month, since a candidate with no opinion about waste has not looked. Ask how many accounts each specialist carries. Ask what their creative capability is, because on the automated social platforms creative is most of the remaining leverage and a pure media buying shop will quietly need you to supply it. Ask about compliance review of ad claims, since the FTC's advertising guidance applies to the claims in your ads regardless of who wrote them. And ask for one client who left and why. The willingness to answer that question is itself informative.
Questions people ask about digital ad agency
Percentage of spend or flat fee?
Flat or hybrid for most advertisers, because it removes the incentive to grow budget for its own sake. Percentage models can be fine with a cap and a floor, and where spend genuinely drives workload. Whichever you choose, compare agencies on the absolute fee, not the percentage, since the percentage hides the number.
How many accounts should my specialist manage?
Fewer than you fear. There is no universal number, but ask directly and compare answers across candidates. A specialist carrying a very large book will be reactive by necessity, which shows up as accounts that are maintained rather than improved. The question is rarely asked and almost always answered honestly.
How long before I can judge performance?
Long enough for the platforms to gather conversion data and for creative testing to run, which for most accounts means a couple of months minimum and longer at low volume. Judge the first month on setup quality, tracking accuracy and waste removed rather than on results the data cannot yet support.
Should the agency also make the creative?
On social, ideally yes, or you become the bottleneck. On search, creative is copy and testing rather than production. If the agency does not produce creative, be explicit about who does, how many assets are needed each month, and what happens to performance when that supply runs dry.