Well, for what it's worth here's my input.
No dog breed is without some potentially negative points and there can be individual exceptions to all the generalisations I've made about each breed.
Your lifestyle seems to indicate that you need a low energy dog breed. In that case, I strongly advise against Border Collies, Aussie Shepherds, Blue Heelers, and most herding dogs. They are great dogs but they are usually very high energy dogs. It's simply not fair to the dogs to not give them the exercise they need. The number of dogs I've seen that have become neurotic through insufficient exercise is very sad. That said, they make great Agility dogs and if you can give them enough exercise and mental stimulation then they're awesome to see at work.
Labs and Boxers are great dogs but also require regular exercise...especially in the first 2 - 3 years. I'd classify labs as a medium energy breed. Boxers a little more active than labs. They do shed too.
If Labs appeal, but shedding is an issue, then look into Flatcoated retrievers instead. Longer hair, but they shed less than labs because they don't have the thick undercoat. They are similar in energy to a lab. However, they are very people oriented so if you don't want an indoor with-the-family pet then this is not the breed for you.
Golden Retrievers are great, moderate energy, family pets too. However, Golden Retrievers and Labs are both victims of their own popularity (as are German Shepherds). Unless you spend a lot of time checking out the background of a breeder and their ancestral line, far too many suffer genetic health issues thanks to endless puppy mills pumping out as many as they can. Examples include hypothyroidism, allergies, hip dysplasia etc.
Oddly enough, some of the large/giant breeds are actually medium or low energy dogs. Great Pyrenese, English Mastiffs, and Bernese Mountain dogs are fairly sedate once they reach adulthood and make good family pets and are good watchdogs. If you socialize them well from an early age, they are not aggressive to people although they will bark at people entering the property. Be aware that Giant breeds live shorter life spans and are prone to some cancers such as Osteosarcoma. Given your yard space though, these may not be the best choice.
Bloodhounds are, surprisingly, quite low energy dogs and make great family pets. However, they do have a powerful tracking instinct and their nose can cause them to go walkabout. Also, as with any 'wrinkly' dog, you need to be prepared to spend a lot of time on skin issues: you need to be prepared to clean out the folds on the skin routinely or risk potential infections etc.
Terriers are some of my favorite dogs but they do have their down sides. They dig. A lot. If you are a gardener or want a perfect lawn then forget it. They are small but they are like energizer bunnies and need regular exercise. They are inclined towards aggression to other dogs and this needs a lot of work in puppyhood to overcome.
They can also become snappy with young children: this is also true of most toy breeds like Maltese, Bijon Frise, Chihuahua etc.
My favorite terrier breed is the Norfolk/Norwich terrier which tend to be less dog aggressive than most other terrier breeds. Hard to get though. Border Terriers are also good choices.
Whatever dog you choose here's some advice:
1. Socialise your puppy as soon as you're able to take the puppy into public (after shots). Introduce your puppy to a minimum of 100+ friendly strangers within the first couple of months. Take a bag of tiny treats to give strangers to give one to your puppy. After a few days of concerted effort, your puppy will come to /love/ people.
2. Introduce your puppy to as many friendly dogs as possible in the first year of life. Dog parks can be great but be careful if you seen unbalanced/aggressive dogs in the park and don't go in if you see problems between dogs.
3. Read a book on dog training. I'd recommend 'Good Owners, Great Dogs'. It teaches you to 'think dog'.
4. Go to as many dog training classes/puppy kindergartens as you can.
As for buying from a breeder or getting a rescue dog, it's a risk either way. I'm sorry to quibble but rescue dogs cannot rationalize like people: they do not understand that you rescued them and decide to behave in eternal gratitude as a consequence. Often times, rescue dogs have come from a bad home and have not received early socialization and proper training. Even if they behave ok in the pound, problems usually arise one the dog has become a fixture in the new home as they begin to decide that it is their new territory. Which is not to say rescue dogs aren't a good choice. Just be very careful. Also, pure breeds that are found in rescue situations are not necessarily a good bet. Dogs that end up in pounds typically were obtained by owners who didn't care much about the dog. Such owners are usually the ones who buy from puppy mills. Dogs produced by puppy mills are far more prone to genetic disorders and inbreeding than those produced by responsible breeders.
You may get lucky, you may not. There is also a myth that mixed-breeds benefit from outcrossing (or hybrid hardiness). What you typically get is entirely unpredictable and is usually a mix of the problems of both species. This is partly because if it were easy to get rid of genes that cause the problems by outcrossing different lines of dogs, it would have been done long ago by the early breeders of each breed. Which is not to say that there aren't some awesome mixed breed dogs: just that there really isn't much health advantage in selecting a mutt over a pure breed (unless its a puppy mill-produced pure breed).