IRS has a great Small Business web page at IRS Business. Check out starting, operating or closing a business at Start/Close Business. Also, check the latest business news that gives small business owners information about the latest mileage rates, worker classification (employee vs. independent contractor) and other announcements See Business News. Get the IRS information on business expenses at Business Expenses.
But as always, remember this is IRS general information. For a more in-depth research and analysis check with your tax attorney or accountant.