Have you looked at Sheltie rescues in your area for a sheltie? You can search google for sheltie rescues in your area if you don't know any.
Petfinder is awesome for such things
http://www.petfinder.com/
I always dreamed of having a beagle since I was young so I started looking at breeders and such but I discovered that there were so many beagles currently without homes that I knew I had to adopt a rescue. I actually fell in love with a beagle mix and she is an awesome dog. She also has a great story in that she was living on the streets, without a home, but now she has one.
If you are determined to buy from a breeder, I'd recommend making sure you can visit the breeder and see how your dog has been bred. Often bred dogs aren't socialized properly and can be over bred so that they have issues later on in life.
Other than that, I haven't had many experiences with shelties. There is a sweetie that visits the dog park that is a sheltie (rescue) and is an awesome dog.