Sounds like an interesting research assignment. I am sure many here will be glad to offer you assistance. Here are a couple of good sources that may help you to gather and organize data.
The International Carwash Association may have some valuable info for you at their website;
http://www.carlove.org/index.cfm
Also, the SBA Training & Counseling Partners at the U.S. Small Business Administration would also be a good starting point.
Los Angeles District Office
330 North Brand, Suite 1200
Glendale, CA 91203
(818) 552-3210
http://www.sba.gov/ca/la/
If you need more info just shoot me an email at;
canna@verizon.net