This definitely sounds like a scam. I wouldn't even bother doing any research on this one. Just the mention of Western Union should stop you from reading the ad. To check others out, you can go to a site called
www.reversephonedirectory.com and put in a number (or address) and it will give you a name and address. Once you get an address you can do a search with the County Tax Records and it will tell you who owns the house and when they purchased it. If they rent, you could contact the landlord with this information and ask some questions.
I know when I check myself out, my name and address appear with my phone number and it's not a cell phone and the property tax roll shows that I have owned my house since 1990.
Even when it's not a scam you are definitely better buying local or physically going to pick up the puppy.