You cannot buy a husky. If you join Dawnguard you can get one to follow you, but thats it.
You need the Dawnguard dlc.
Then, when given the opportunity, you need to join the Dawnguard faction. And after doing a few missions for them, look around Fort Dawnguard and find the Husky pens somewhere in the back, near the training room for the two new female recruits. You'll see the two huskies, Bran and... something other. Speak to them and recruit only one at a time, as a pet follower.
How to covert a husky into a follower? Not named ones, the spawned huskies with console commands? I'm trying to make them my followers.