i think you have to go with your gut feeling - if something doesnt feel right then it probably isnt.
When i got my lab, the breeder had 9 dogs of her own - who were kept in kennels outside, but they were working labradors (as in the sense they were "worked") so i think this is fairly standard. She had had two litters of pups within a week and had 18 pups for sale. However, at no point did she rush me to make a decision, although i didnt check the kennels she bought the mum and dad in and both were in excellent condition. The three pups she bought in were all confident, clean and happy, and i felt very confident that they were all well looked after.
I bumped into one of Kira's 1/2 sister a couple of months later, and the breeder had given a number of the puppies to the police force for them to train for various tasks, which apparently she had done in the past. She had also kept the pups and extra 3 weeks so that they did get bought as christmas presents.