Wantadog - you accuse people on this thread of making assumptions based on very little information, but it seems that you have very little information about this dog - or at least, you haven't said here that you have any information about the dog other than the breed.
So - have the pup's parents been hip scored?
What about the neuropathy that another poster mentioned - any history of that in the breed line?
Will the breeder be insisting on a home check?
Is the breeder registered with the relevant breed club?
What will happen to the puppy if it doesn't work out with you - will the breeder take them back?
I think that you need answers to these questions for the puppy's sake. If you love this animal and genuinely care for it, then you will want answers to these questions.
When we decided to get a labrador, my first point of contact was the labrador club of scotland, and their puppy coordinator put us in touch with the owner of the puppy we eventually bought. When we visited the breeder the first time, she showed us all the relevant paper work - KC registration of the parents, their hip and eye scores etc. We also saw the mum with the puppies, and saw their older sister - same parents, born a year earlier in the mum's only previous litter - so we were as confident as we could be that we were getting a healthy dog and were not feeding the puppy farming business.
In fairness, I should say that the breeder did not insist on a home check, but did spend a long time talking to all of us about caring for the dog, and about dh's experience of keeping a dog before. I got the clear impression that she had enough people wanting the puppies that she could afford to be picky, and wouldn't have let us have the pup if she hadn't been sure we were going to be good owners.
Please listen to all the good advice you have been given - for the puppy's sake.
I do think that a reputable breeder would be willing to hold onto the pup for you until you were settled in your new home, and that would be a far better thing all round. No risk for you from breaching your tenancy agreement, and the pup wouldn't have to cope with the upheaval of the move - and it would be just as much of an upheaval for the dog if you are only moving two streets away as if you were moving to the other end of the country. I think you are deliberately down-playing the level of upset this will cause the puppy, and should be more realistic - again for the puppy's sake!!