This is Buddy when he was about 6 weeks of age. He was a bit bigger when he came to live with us, about 8 weeks of age.
Some places will sell dogs this young, as little as 6 weeks of age. But that is one of the things we liked about Annie, that she keeps her pups a little longer, giving them extra time with their mum.
Being with their mum and littermates longer helps a pup to learn how to be a dog and helps them to learn social skills. Annie usually keeps the puppies with their mum until about 8 weeks.