When is the right time to delegate work tasks to another person?

My environment consists of many solo founders.

However, when I see someone is already starting to hire an employee, the question crosses my mind:
What profit has that person achieved when they can afford to pay another extra person?

In some cases, I have seen a call for volunteering, but now I have a purely interesting employment relationship.

Is it determined by the turnover or profit multiple from a given project?

How did you determine the right time for hiring the first employee?