This lecture series specifically talks about the different problems faced at various stages of scaling, and it includes a lot of reputable people who have actually done it:
I'm not actually qualified to answer your question, but it sounds like you haven't discovered a bottleneck in your business yet, and until you do, you probably shouldn't hire any employees.
https://www.youtube.com/watch?v=s3RrVmv5WwA
The YC series is of course good too:
https://www.youtube.com/watch?v=CBYhVcO4WgI
I'm not actually qualified to answer your question, but it sounds like you haven't discovered a bottleneck in your business yet, and until you do, you probably shouldn't hire any employees.