How do you decide between building an in-house team and using an agency?

Frame it as a decision about permanence, specialism, and control.

Build in-house when:

• The work is ongoing and core to the business. Anything you do every week is cheaper and better done internally over time.
• Deep product and customer knowledge matters. Agencies rarely acquire the domain understanding an in-house marketer builds.
• You need speed and responsiveness, without a brief-and-approve cycle.
• You want the knowledge to accumulate rather than leave when a contract ends.

Use an agency when:

• You need specialist skill you cannot justify hiring — a technical SEO audit, a video production, a market entry.
• The need is temporary or project-based, such as a launch.
• You need capacity quickly, faster than hiring allows.
• You want breadth of experience across many accounts, which a single in-house hire cannot provide.

The hybrid is usually right: in-house owns strategy, brand, and the always-on channels; agencies supply execution capacity and specialist skills.

Note: The failure mode worth naming is outsourcing strategy. An agency executing your strategy works; an agency deciding your strategy means nobody internally understands why anything is being done, and you cannot evaluate their performance. Keep the thinking in-house even when the doing is not.