Like Deb mentioned, there is not much info on the website, so I would definately ask lots of questions. The one thing I did see that is kind of a red flag for me would be the number of litters they have had in recent months--5/1, 5/20, 6/1, 7/1, 7/10. That's 5 litters in a 3 month period.
Also, the pups on the home site that the man is holding do not look like Yorkies...they look like another breed, but I don't see any other breeds mentioned on the site?