The moment to stop being only a freelancer

The honest signal is that you are turning down work you could deliver, repeatedly, because your hours are full. Not that you are bored, and not that an agency sounds more impressive.

The second signal is that your rate has stopped moving. A freelancer earns hours times rate, and both have ceilings. An agency is the decision to earn from other people's hours too, and it is a different business rather than a bigger version of the same one.

What actually changes. You stop doing the work and start selling it, checking it, and keeping people busy. Many excellent freelancers hate this and discover it after hiring somebody, which is expensive for both of them.

Ask yourself honestly whether you want to manage, because that is the job. If the answer is no, the better path is raising your rate, narrowing your specialism and staying small, and that is a legitimate destination rather than a failure to grow.

The alternative in between is a network of trusted contractors you bring in per project, which gives you capacity without payroll and is where most small agencies genuinely start.

Do not hire to fix a slow month. Hire when the pipeline is reliably beyond you, because a hire is a fixed cost against income that is not.

And start from profit rather than revenue, because an agency with three people and the same take home as your freelance year is more work for the same money, which is the commonest outcome.