Thanks for replying, Mert. After reading your advice to read about the pluses and minuses of certification, I have been digging through the archives. I'm still not sure if I will go ahead. As I said, I will not be able to do a lot of shops over the summer, so I have a couple months to consider certification before I start trying to make this a "full-time" job.
I think the certification sounds very similar to what happens in the doula world. Pretty much anyone can get a certification (of course, they are more costly than MS certs!) and put up a website, but some of those folks are still pretty lousy doulas!
All the best. For now I'm having lot of fun doing these shops. Hubby just wishes I would actually get my first check.