WHERE
There are many options available to you for welcoming a dog of any age into your life. I am a fan of rescue, and within the world of rescue there are many many roads to take. There are high-kill and no-kill shelters, as well as organizations dedicated to specific breeds. All of these are run almost entirely by volunteers who are devoted to homeless pets.
If you want a Border Collie puppy, there are Border Collie rescues who have puppies. Many rescues list their pets available for adoption on websites like PetFinder.com as well as individual rescues having individual websites like Almost Home (almosthomeanimals.org), from whom we adopted Foster Dog, or Best Friends Animal Sanctuary (bestfriends.org) in Utah where my sister and I volunteered in 2009. Wherever you live, and whatever kind of dog you would like, you can find a rescue to help you.
Rescue doesn't mean free. Adoption fees are a fraction of the costs incurred in rescuing, healing and caring for homeless animals, and rescues fundraise for these expenses, but your application and/or adoption fee helps tremendously. There is never enough money available to them to rescue and care for all the dogs who need them. Some people criticize other avenues of canine adoption. I will not do that, especially here, but I'll type again that I am a BIG fan of rescue!
Breeders voice their dedication to high standards of conformation and temperament of particular breeds of dogs. Most breeders are passionate and devoted to dogs, but of course, there are unscrupulous breeders who make a lot of money off of people's inability to, or lack of, research. Luna, whose first owners purchased her from a breeder, has two birth defects that veterinary specialists informed me would not have been first generation defects, meaning the breeder from whom she was purchased was not dedicated to the health and standards of Labrador Retrievers. We didn't care, but Luna is one example of how "breeder" doesn't mean "reputable."
Pet stores are another option for adoption. They are controversial as potential supporters of puppy mills which are commercial breeding centers operated for profit with little to no attention to canine welfare. Dogs suffer horribly in puppy mills, and many people believe no reputable breeder would every supply puppies to a pet store. I have done little research on this myself. In my opinion, it is up to dog owners to do the research, and to do more than you think is enough.
Breeders and rescues often have lengthy application, interview and matching processes with policies for you to return dogs to them if the adoption is not successful at any time. They would rather you return the dog to them, even years later, than for you to abandon it or drop it off at a kill shelter.
WHEN
I recommend volunteering at a shelter, dog-sitting, or fostering an adoptable dog to learn about your readiness and ability to include a dog in your family life. Something some families don't consider is preparing a budget for their new family member. There are several variables in adding to your family, and I think it is important to consider the potential expenses.
Will you feed your dog high quality food that can cost $1000 per year? Will you take your dog to daycare or boarding which can cost $25-$30 or more per day? Do you know how much an average veterinary visit will cost? Just some things to consider.
I was in deep grief after Koko and Satchel died within one year of each other. It was frequently suggested that I get at least one other dog to help me cope, but I didn't think I was ready. Many people have success adopting a dog the very day after they say goodbye to one. I felt I'd be a more focused Pack Leader if I lived through, and with, some sadness for a while. I cried for about eight months and then Foster Dog came into our family.
Our where and when worked out wonderfully for our family. I hope you are on your way with the Who What Where & When. The Why and How are still to come!