I have talked with several people who do this on smaller scale like me. Alot of people have a little niche of some type. One guy has access to cheap by product feeds. Some work at stock yard. One has acsess to trucking better rates. Couple are retired more time to deal with it. My wife is a vet better med pricing.
Alot of money can be made backgrounding calves. Its just not as simple as one would think that has only dealt with cow calf and keeping there raisied calves 90 days after weaning. Alot of it is taking others people calves that were half ass weaned. And fixing all those problems mixed together. And making a correct 50k# package. The time is probley what i like the least. I'm full time tobacco farmer. When i go down there have to pull 5 or 6 sometimes messes up whole day. And with these prices ties up alot of money. But when it all works almost nothing like return wise.
If you get it going one piece of advice I will give is. PI test every single one pretty quick when you get them. Some people don't and won't. I promise it's worth the couple bucks. If and when you get a positive get them out of the group quick. And, don't do this back grounding thing nose to nose with your momma cows.
It's amazing how much you learn about cattle. When you start buying high risk bawling calves to comingle. I had been around beef cattle my whole life. This was very eye opening.