A good book you can use to get started is called Business Information Sources by Lorna M. Daniels and published by the University of California Press. The U.S. Department of Commerce publishes some great pamphlets, such as U.S. Industrial Outlook. Trade magazines should be very helpful too. It also doesn't hurt to simply go out and speak with some business owners yourself. Especially if you make it a point to do so in a city other than your own, so that you don't seem like competition, you will likely find them to be quite willing to help you out.
People love to talk about themselves.
My problem is that my credit is not good and I cannot find a bank that will extend me credit. Talk to your bank about these types of loans, and if they can't help, go to another bank. This revolving line of credit is based upon your accounts receivable. Purchase order financing. Fixed asset loans.