Every founder reaches the point where the informal HR that worked at ten people starts breaking at sixty. The question is not whether to build an HR function — it is what to build first.
In most growing companies the right first move is an HR Audit: a clear map of what you have, what is missing, what is at risk and what to fix first. You stop guessing, and you build in the right order instead of the loudest one.
Compliance and a basic policy foundation come first — they carry the most risk. Performance systems and culture work follow. Built in the right sequence, each piece reinforces the next.