I've struggled with this over the years also. Back in 2009/2010 I was supplying 29 wholesale accounts on a regular basis and I had a baby underfoot, so I had to hire some help!
I tried many different avenues, paid interns, friends, a private contractor in another state, and two low minimum smaller scale factories. I had issues with all of them... My biggest issue was letting go of complete control and not being completely satisfied with other peoples sewing skills ~ after all it's my name on these garments!
If you can find a production facility that will take smaller minimums (like 100 or under) it can be a lifesaver for simple items or basic shells. For instance I had a shirt design that I was embellishing, so I bought all the fabric, made the patterns (they will require you make the flat patterns so they can cut them with the fabric saw) and they produced the basic shirt. I then did all the embellishing at home and shipped them out. Same with skirts, they made the basic skirt, then I added the embellished pockets, trims etc. Expect that the factory work will take a long time to get done, probably 3-4 times longer than it takes you, and you can expect about 15-20% to be sewn completely wrong! At least that was my experience with both companies I used.
I had many part time employees that came to my house and worked beside me on simple tasks (my control issues again). Most of them were either friends or friends of friends. They were helpful and if you can squeeze them into your current workspace it's great. Plus they can likely work weird hours ~ a couple hours here and there. I let a few of them bring their kids over and it was like work/daycare :) My issues with my lovely in-home friend employees was, nonstop chitchatting (mostly me!), them showing up late constantly, and having to spend a lot of time teaching, but maybe that was just my group of friends, haha!
I'm currently just working by myself, but I'm only regularly supplying 2 wholesale accounts and I'm keeping up okay, despite having another baby underfoot :) I think if I get to the point where I need to hire again I will look for one or more experienced seamstresses that would work on a contract basis from their own homes/studios. Preferably in the same town, so that communication is easier.
I'm interested to hear what everyone else's experiences have been also.