I'm not saying this to be mean but if that is all you can afford you probably can't afford a puppy right now. I spent $900 in just the last three days in unexpected vet bills and well over $10,000 on vet bills over the life of one of my dogs. My GSD pup has insurance but even that costs more than those pups each month and that isn't full coverage.
Athena -GSD- born 12/13/12
Luna -Shepherd Mix- born 3/20/99