The one thing you need to start a business, besides a good idea, is money. Banks don't lend to new businesses with no track record, no cash flow, and no collateral. So that often means tapping into your savings or turning to others for money to start a business.
Once your business is generating revenue, you need to have a firm handle on the numbers aspect of your business. You'll need to monitor cash flow and understand financial management: bookkeeping, controlling costs, banking, taxes, insurance, accounting, and all financial matters related to your business.