That's a really great question and when I first hired I didn't think I had the money either. We were trying to get someone hired and tested them for half-time.
The biggest thing to know is that the time you get back from your business you're able to make the money to afford the person who is doing the work that you're not doing, then it's an asset and a necessity to moving forward in your business.
I do believe people can hire well before they think they're ready, but the real question is that can you make up the cost of the new hire with the time you get back from hiring them.
If you could easily spend the time you free up to afford to hire that person, then you should do it, even if it's just one hire.