We have an almost 4 yr old BC. You obviously don't need the warnings people like to give about BCs since yours will be a working dog.
Our dog Maverick is that quintessential best dog ever, but almost a different SPECIES than any other dog I've been around. He plays "fetch" with anything-- literally... We have lots of balls we kick or throw for him but he will pick up soda bottles, tubes of caulk, etc-- whatever has your scent on it, and bring it over to be thrown. Has a few weird obsessions that are a BC hallmark. He picked a tree near the driveway entrance at our old house and every time we let him out he might spend 5-15 minutes jumping at the tree and occassionally barking. We moved a year ago and he picked another tree here and does the same thing. He has a fetish about bubbles, the lawnmower, the sprinkler or kids splashing water -- bites at the bubble/grass/water as he jumps and acts generally nuts. (I have to put him up to mow grass b/c it is ROCKY here in Missouri!) Also, obsessed with sticks (thumb- sized up to tree limbs)- carries them all over the place. He is very friendly to anyone who comes on the place, people comment on what a happy and polite greeter he is (doesn't jump etc). Though his herd drive seems high, interestingly, he pays little attenion to the chickens we got this spring once I moved them out of the brooder. I intend to get a few goats this summer but I don't have high hopes for him to work them at his age, but you never know. If he shows an interest I'll have to read up on training!
He spends a lot of time outside but is inside a lot too. Great inside dog-- very calm, just lays around or plays fetch down the hall with a stuffed squirrel. Would spend all day in his crate if we let him (I've heard BCs tend to get very attached to their crates: crate potatoes). He's not a love all over ya dog like a lab, he's more reserved although he does really enjoy our company and if my DH has been out of town he's really excited about his return.
Everyone has an opinion on the pup vs. started dog thing, but rescue is another option you might consider. Its hard to know what pups are going to turn out like. Long established BC rescues will want to help you pick the one that is really best for your situation and the dog you get is a known quantity. There is a great BC rescue in the midwest called MO-KAN Border Collie Recue (
http://www.mokanbcrescue.org/ ) and they have a lot of great dogs in foster care, I'm sure there are similar groups near you. You can meet the dog beforehand, get an assessment from knowledgeable BC people about dogs that might fit, and if it doesn't work out they take the dog back. Just an idea.
Do you have livestock guardian dogs? Just curious, as I am interested in them for us in the future for our goats.