I don't know your situation but if going away to college is in your near future, I would take that into consideration. I am a college student myself and believe me, steady cash flow is not always happening!
Purchasing the puppy is not the only expense...think lots of vet bills, food, toys, puppy pads, etc...
Now that's out of the way...
Yorkies make great pets! You definitely picked a great breed. You might try Petfinder.com or search the classifieds in your area newspaper. I found both of my puppies' breeders in the newspaper.
Hope this helps and good luck with your search!