Border Collie pups with a guarantee to work are going from $350 to $1,000 each. A started dog will cost at least $1,500, depending on who you get it from. A finished dog will depend on how good it is and who is selling it, but you are looking at least $2,500. I know it sounds like alot, but you get what you pay for. A "cowdog" pup at the feed store is not what you want to waste your money on. Open your checkbook up if you want a dog that will be worth the money in the long run.
If you think you can train a pup to work for you, go that route. If you want something to start working right away, get in touch with someone that has some for sale and buy a started or finished dog.
The best thing about a Border Collie is that they are bred to gather and bring cattle to you. Once the cattle realize the dog wins, you can open gates on the way as the dog is bringing and holding cattle for you.
And Border Collies are not as bad as people make them out to be about working stock when they are not supposed to be. It's called making the dog realize when it is supposed to work and when it is not to. I can leave all my dogs out and they wont go work for themselves. I usually just kennel them so they dont get out on a road and in the kennel they just kick back and relax.
If you are seriously interested, I can give you a phone number for a guy in CA that will for sure help you.