Border Collies?

I don't post much here, I tend to hang in the Equine Forum.

My family has a small business doing horses. We live on a family farm. LOTS of horses and no dog proof fences.

I have about 5 acres I could devote to sheep. All I know about sheep is you have to feed one end, and shave the other.

I have always, always, always wanted a working Border Collie, with an eye towards trialing. I bought a puppy 15 years ago, loved him to death, attempted to do some lessons with him and was told that "as a herding dog, he'd make a nice pet". ; ) didn't at the time have room for another BC in my life, so Pip spent the rest of his life herding me, instead. I am more cooperative than sheep, apparently.

Pip is gone now and my almost 5 yo child is finally, finally in school half day, so I feel like I have a little bit more time to devote to a dog.

I'd love to take lessons from someone, I am open to getting an older, made dog to learn with, I don't NEED to get a dog right away if lessons are the way to go....

I'm looking for some discussion on this subject....am I being fair to the dog, living on a horse farm where he absolutely must NOT chase horses? What's the best way to start..find a teacher, find a dog, go to BC rescue and take whatever got turnt in because he was herding SUVs in Yuppieland, get sheep, don't get sheep, etc...

Many thanks in advance to anyone who has thoughts to share...