When you buy a small agency, client concentration is often the biggest hidden risk, because if one or two clients pay most of the revenue, losing a single one of them after the sale can wipe out the profit you paid for. Listings tend to present total revenue and total profit as if they were stable, diversified income, but agency revenue is really a small number of relationships, each of which can end with a phone call, a budget cut, or a change of marketing manager at the client. Understanding concentration before you offer is therefore not a minor due diligence item but the central question of the whole purchase.

Measure concentration simply and without sentiment. List revenue by client for the last twelve months, calculate each client's share of the total, and look at the top one, top three, and top five together. As a rough guide, if the top client exceeds 25 to 30 percent of revenue, or the top three together exceed 60 percent, the business depends heavily on relationships that may not survive a change of owner. Also check the trend: a top client whose share is growing year by year is becoming more important, not less, and a business that added no significant new clients in the last year is more fragile than one with a healthy pipeline, even if their totals look identical.

Check the contract terms behind those top clients next, because the form of the relationship matters as much as its size. Clients on signed twelve-month retainers with notice periods and defined scopes are far safer than clients on rolling monthly arrangements that can end with thirty days' notice, and both are safer than handshake deals with no written terms at all. Ask to see the actual agreements, not summaries, and note renewal dates, termination clauses, and any exclusivity or rate guarantees that could limit your freedom to change pricing or staffing after the purchase.

Ask why the big clients stay, and be honest about how much of the answer is the founder. If clients stay because of a niche expertise the team delivers, a proprietary process, or results that are documented and repeatable, the relationship has a good chance of transferring. If they stay because they trust the founder personally, enjoy working with one individual, or have a long social history with the seller, that loyalty may walk out the door with the seller, however warm the introduction meeting feels. The test is simple: would this client stay if the founder disappeared for a month, and what evidence, such as team-led delivery or multi-contact relationships, supports your answer?

Look at churn and replacement history as well, since past resilience tells you something about future risk. An agency that lost a major client last year and replaced them within a quarter shows it can win business without the founder's personal network, while an agency that has never lost a client may simply never have been tested, which is not the same as being safe. Ask how new clients are won, who wins them, what the sales cycle looks like, and whether the pipeline is documented or lives entirely in the seller's head, because a business without a repeatable way to win clients will shrink steadily if its largest client leaves.

Price concentration risk honestly rather than hoping it away, and use deal structure to share it fairly. Options include discounting the valuation to reflect the risk, asking the seller to introduce you to top clients before closing so you can judge the relationships yourself, or tying part of the payment to those clients remaining for six or twelve months after the sale. A small agency can still be an excellent purchase with concentrated clients, but only when the contracts, the team, and the price all reflect that risk instead of pretending the revenue is as stable as it looks on a spreadsheet.