My sister has a 6 month old BC.
He is a fiend.
He is the fiendiest puppy I have ever known. She calls him Motocross; I call him Demonspawn. Why she got him, I'll never understand--there were BC's at one of the dairies my grandad worked at when we were kids, and she knows what they're like!
He has utterly corrupted her shepherd mix Squig, who is almost 2 now, and used to be a reasonably good dog, for a girl whose mom worked full time and whose dad drives OTR 6 days a week. She was neither a digger nor a house tearer-upper, until the fiend came. She never even TRIED to get out of the yard until the fiend came.
Now, my sister comes home from work and finds them OUT of the yard at least once a week. He's almost...Siber ian...in his determination to escape. He can't be left in the house, he's chewed thru three crates and can open the refrigerator--OH, yes, he loves to make a mess. He also has a taste for underwear. And he rarely shuts up. The neighbors hate him.
None of that is irremediable. BUT, and it's a really King Kong sized BUT...
You have GOT to have a LOT of TIME and a lot of energy to work with a BC. Demonspawn has my poor sister worn to a frazzle, and I don't know how she's going to survive. She may have to give up and send the creature to my mother; Mom's retired and has time to deal with his behind. Maybe when he's, like, 12, my sister could take him back.
My experience with BCs is this: if you have HOURS, and I mean HOURS, to spend working with pup, really focusing on obedience or specific jobs and keeping pup challenged all the time so that they don't have any chance to get bored, then a BC might be the pup for you. But you HAVE to watch them every minute, at least at this stage of the game. And this stage of the game lasts from 9 weeks old until about 10 minutes before they keel over from old age.
But if you have to work to support your dogs, I'd look for a breed that's a little less...driven. If you really want a working breed, I'd go a little bigger than a BC and find a really good German Shepherd line (not easy) or maybe find a Shiloh Shepherd breeder (lots better oversight of their breeding lines than Germans from what I can tell researching them.) Shepherds are just as smart, just as much fun, and will play all the same games as a BC, but in my experience, they're much more patient and forgiving with you, and behave better on their own while you're out earning the food money.
I have a number of friends who have or have had shepherds, or shepherd mixes and once they're beyond the puppy stage which is challenging no matter WHAT breed you get, my observation is that they're a lot more trustworthy behaviorwise than a BC. With the shepherds I've known, if they get bored, they'll generally take a nap, rather than tear up the couch or dig you a new pool.
