If the company is private, little or no specific financial information beyond sales figures may be available about the company. Try to find articles via the databases below. These contain thousands of full-text newspapers and business periodicals; you may be able to locate articles which quote company officials discussing the firm's finances.
Our best database for VC information is CB Insights.
Also, consider using ratio books. They will allow you to create your financials using industry averages. Several Cornell libraries have the print copies of these recommended books:
Are you just starting to become familiar with the term "balance sheet"? If yes, you might want to read Merril Lynch's excellent presentation "Understanding Financial Reports."
Public companies are required to file detailed reports of financial activity. In the US, these filings are available directly from the SEC (the Securities and Exchange Commission), or via the selected databases listed below.