5 weeks is a little early, honestly. 8 weeks is the preferred minimum, 10 weeks being best. Even though the pup is weaned and eating dry food, they haven’t yet made this their established diet and will often still nurse. Also, being taken away from their mother and from their sibling pups can cause behavioral issues later in life, such as inappropriate biting. This is a crucial time when puppies learn the consequences of biting, and other sorts of behavior are acceptable and what will not be tolerated in the "pack". If you already got the puppy, then just do the best you can. Usually with proper care and attention, puppies that are separated and this young age can still be really good dogs. Good luck. Also, don’t forget to vaccinate!