You mentioned a yard. A yard is good play, of course, but not a place to stay while you are gone (doubly so if a puppy). Yards have way too many troubles to get into, fences to dig under, and people to come steal them. An older dog might do fine with that, maybe even a doggy door, but not a little one or teenager. Not sure if your intent was to leave the dog in the yard or just use it to play but thought I would mention.
Don't solely focus on a pup. There are many great options, especially if this is your first dog. Rescuing an adult could be an option. My Melli is an older rescue (probably about 6 when rescued) and I trained her from basic through her CGC and an accelerated easy agility class. If she weren't so darned carsick I would have gone into scent work and likely would be competing with her. Breeders often have older dogs or pups that didn't work out for show or breeding. Their personalities are set and they have had foundations laid by someone who knows dogs. Starting with a little puppy, while cute, is horrible work. I always say the best thing about having a puppy is the photography. After that, it's endurance until they are about 5-6 months old when they start to really become fun. As a little pup, first they must be socialized / exposed to the world properly while not being exposed to illnesses in the area (I live in a very high parvo/distemper region, for example), they must be potty trained which requires some dedication, they chew and ruin things, they are expensive with all the shots and vet visits, and so on. Puppies are fun, but you have to know how to raise them. My very first dog ever was an Aussie. He was about 2 years old and a rescue. Couldn't be closer to me or more perfect. I wanted a dog that knew more about being a dog than I could teach. Dogs, 1, 2, 3 were adults and rescues, as was dog 5. My 4th and 6th dogs were puppies. I made some major mistakes with the first puppy from choosing through missed clues to fear periods to personality traits I could have curbed early. My 6th dog, Cubby, I did right and he's a great little guy and best overall package of any dog I have had. I also became a dog trainer while raising this one. DO consider an older puppy, a breeder placement, or a rescue in your equation. I don't mean to discourage you from getting a sheltie in any way, or any other dog for that matter, just consider all the options at your disposal.