If it's a silkscreen printing shop, you need bigger space and more manpower since it's quite labor intensive. You also need time to train your people because silkscreen printing involves some learning curve and requires skills and experience.
If digital printing/heatpress, a higher capital for good equipment is needed. The quality of print will depend on the quality of your materials and equipment (e.g. China vs. US).
For any type of printing business, you need graphic artists or someone knowledgeable with Photoshop, Illustrator, etc.