Hile most companies farm out the work. There are really 2 way for you to do it. 

First- buy several sewing machines and hire about 6 people. 1 - person to do the cutting out, 1 -  people to pin togeather, 2 - people to run the sewing machines 1 - person to wash /dry and iron. 1 - person handling the shipping and receiving. That will cover your first shift and understand that is minimal.

As for the second way it will need about $2 million to buy the automatic equipment.