Insurance and a good accountant.
What kind of business? NDE?
You will need a few months of operating cash until you start receiving from your invoices unless you can get paid quick. I get paid 30-45 days after I invoice.
Regardless of the type of business the insurance and IRS burdens weigh heavily on small businesses.
Quickbooks software helped me to be able to handle the financial records.
Oh yea...you will need lots of good, paying customers.