As Lillium said, you have to consider the cost of owning a dog over hopefully a fifteen year lifetime. If you are struggling with the purchase price, you are not financially ready for a dog.
Please do not make the mistake of buying a "bargain" puppy for a few hundred dollars. More than likely it will have inherited health problems that can run into the thousands to correct like liver disease, luxating patellas, to name a few.
Here is a sobering article about the cost of owning a dog. It's a pretty conservative estimate IMO.
http://www.peteducation.com/article....articleid=1543