usually dogs in rescue have been vetted and well checked over for problems, so at least you are well aware of what you are dealing with beforehand.
Here are some more options
www.unitedyorkierescue.org www.yorkierescue.com www.sosdogs.com www.yorkshireterrierrescue.net www.barkbytes.com/rescue/yorkie.htm
Cheap yorkies are generally no bargain in the long run. If 400.00 seems like too much you may want to reconsider a yorkie for a pet right now. Care expenses are not cheap and vet bills can be astronomical ..and unexpected.
Best of luck in your search.