go 100% with a reputable breeder. Are you looking more for a "show dog" type or an actual working border collie?
find a border collie forum, start doing your research now. Well in advance of when you think you'll want a pup. It's not unusual for reputable breeders (farm OR show) to have a waiting list of people who want their dogs. That also gives you plenty of time to shop around and for the breeder you pick to get to know you better. They should ask you a hundred million questions so that they can match you with the right puppy. If the breeder just says "$XXX come over and pick one out" run away.
Honestly, breeders have an undeserved bad rap. Sure, there are some people who are just into it for the money and then there are the puppy mills. A good breeder is going to have a solid contract and one of the things you will always find is a return policy. If you find yourself unable to keep the dog for any reason, even 10 years from now, they will take the dog back. (Some breeders use "right of first refusal" which means you have to contact them before you are allowed to find the dog a new home. They will screen the people and make sure the dog is going to a good place.)
Good breeders support rescue. They might volunteer time or money. If an older dog is a better fit than a puppy (or the home isn't a good fit for their breeding), they will refer people to rescue. That doesn't mean that you will NEVER see a dog from a good breeder in the pound, of course. Because people will sometimes toss out the dog despite the contract. BUT, they will go pull the dog themselves when they are contacted. Of course, this is the reason that they ask those hundred million questions. A dog that is a good match for a family is much less likely to be rehomed. A family that has a good relationship with the breeder is more likely to seek their help if things DO go wrong.
You aren't just buying a puppy from a reputable breeder. You are also getting a lifetime of support. My boy is 10 months old. I talk to his breeder at least a couple times a week since we are on a few of the same forums. My older dog is 8 years old. I'm still in contact with his breeder a couple times a year. Both have always been a support system though the trying puppy stages, training questions, health concerns. And, of course, love to hear brags and updates about how the boys are doing.
Health testing. every breed of dog has some type of health problems. Yes, even mutts. Find out what ones are in your breed and what tests are needed. Don't go with a breeder that skimps on the health of their dogs. "The vet says she's healthy" doesn't mean anything since these diseases are genetic and can be passed on even if the adults don't have symptoms. The breeder should be able to discuss not just the parents, but the health history of every dog going back several generations. Also brothers/sisters/aunts/uncles
If you are looking for a "show type" border collie, then you are going to want a breeder who actually SHOWS their dogs in conformation. Skip the breeders who show you the pedigree with a few winners scattered here and there. What have the PARENTS done? Why are they good dogs to breed? Just because my grandma was a beauty queen doesn't mean my kids will be!
If you want a working border collie, then you're going to need a breeder who works their dogs. Some breeders do agility. Or flyball. Or other sports. Some do herding trials and have the titles to back that up. Some people are ranchers who work their dog on their own stock every day. Those people might not have titles or certificates hanging on the wall, but they can take you out in the back yard and show you what the dogs are capable of.
Likewise, you have to know what you want. Talk to people whose BCs you admire and find out where they got the dog.
The good breeder can tell you not only what the parents have accomplished or even the grandparents, but brothers, sisters, cousins, aunts and uncles.
The good, the bad, and the ugly. A good breeder isn't going to just gush about how awesome their dogs are. They're going to tell you about all the shedding. And the bathing. And the mud. The amount of exercise. How much sleep you're going to lose when the new pup comes home. They're going to want to know what kind of experience you have with the breed. What training you are going to do. What activities (a BC is going to need a job) you plan to do. And, if they don't think you are ready for a BC, they are going to tell you that to.
