Does anyone out there breed or know a lot about Shetland Sheepdogs?

I saw a puppy that is really young yet. It is purebred AKC and both parents have excellent sable markings. This pup is solid sable with a tiny white snip. Would this pup be allowed to be shown? I thought I read that as long as there is not too much white, that it's acceptable. Is this rare? It is really cute. They are selling it as pet quality.