Usually any time after 7-8 weeks. Many states have regulations regarding minimum age. However, your individual circumstances must be considered. Do you have the time to spend with a very young puppy? Will someone be home to housebreak him? Would an exuberant 6-month old puppy overwhelm a tiny child? Or would he be better matched with a 6 year old youngster? Remember too that the puppy under 3 months needs lots of time to rest. Don’t forget that adult dogs, already trained and generally calmer, also make ideal pets.
While much can be told at six to eight weeks about the puppy’s eventual looks, if you are seeking a show prospect you might be better off waiting until the pup is six to eight months of age. At that time, be prepared to pay a higher price for all the additional time and effort that the breeder has spent raising the show potential Boxer.