Suggestion:
The website I use for the valuation of a going business is BizBuySell. The have about 50,000 businesses of every color and description across the whole United States listed for sale. Some listings are very detailed including gross sales, net income, etc., etc. For about $40 (that's good for 2 months as I recall) they will also generate reports for you with comparables of past sales, where you can modify the parameters as often as you wish. Here is their link:
http://www.bizbuysell.com/content/main/
