Most owners ask this question about two years after the answer was yes.
Hire too late and you pay for it in cash flow you did not see coming, growth you could not fund, and decisions made on instinct that a model would have settled in an afternoon. Hire before there is anything to analyze and you are paying for a conversation you could have had over coffee.
The useful question is not how big the business is. It is whether the cost of getting the next decision wrong has passed the cost of getting help with it. Below is how that plays out by stage, and the signals that say now regardless of stage. If you are still working out what the role covers, start with what a business financial advisor actually does.