How to Reduce Vendor Expenses?

I'm doing a research paper for high school hoping that this will help me start my own business and I wanted to ask what are your biggest monthly expenses when it comes to vendors? (payroll service, insurance, POS system, etc.)

Or what services do you require to keep your business running? (internet/phone, shredding pickup, etc.)

Sorry if this is a bit vague but I'm trying to identify where businesses spend the most money with vendor services.

Thank you,
Andy