The short answer
The trigger is not a revenue number, it is where the pain is landing. If your sales leader is spending most of a day a week in spreadsheets and CRM admin instead of coaching and hiring, you are already late. Before you have found go to market fit, a fractional or agency RevOps setup is usually the right call, because a full time senior operator has nothing stable to systematise yet. Once the motion repeats, hire a Director level person in house who can own the systems, the data model, the forecast process, and planning, and who has done it at a company one stage ahead of yours. Do not hire junior first: a junior admin will keep the lights on but will not fix the process, and process is what you are actually buying.