Since huskies were bred to basically jog at a quick clip, personally I think they should be able to start building endurance by 6 mo old or so. if i remember correctly, Keiko was pretty much full grown by then anyway, just hadn't built up any muscle yet.
Of course I would not recommend putting them behind a sled at that age but jogging should be fine. Huskies are a lighter breed that were bred for just that. I would however have her hips checked previous to make sure they won't be a problem.
For a young puppy, short walks are best. At least until they are properly leash trained. And she should start right away b/c as you know huskies have a propensity for pulling. I figure a couple of blocks at a time should be good until she gets what walks are all about.
By 4 months old, I was taking Keiko on mile long walks or longer......al though not every day. By the time she's 6 mo old she should be able to handle several miles at a time provided her endurance has been increased.
I can't wait to see some pix. I love husky puppies and all their fluffiness!