You can make money when not playing by automating different areas of your operation.
When you collect enough Cash you can hire Managers by tapping on the shadow-like silhouette, Managers allow you to automate the different Units (Stockroom, Section & Market).
Tapping on the green button reading Hire will activate your Manager and automate the Stockroom Unit for you.
*Default Managers do not have boosts
You should repeat the process for all 3 Manager Slots to fully automate your operation.