The tell-tale signs
You are signing contracts without review. Legal questions are piling up. A dispute has caught you by surprise. Decisions with legal consequences are being made without advice. Any of these suggests you have outgrown ad-hoc support.
The right moment
The right time to bring in a fractional general counsel is before something goes wrong — when the business is growing fast and the legal risk is rising but a full-time hire still does not make sense.