I have allways made money with my cattle and pigs. Even if they didn't place high enough to sell in the auction I entered them in carcass and got paid for their meat.
I assume your talking about the animals. At our fair cattle cannot be older than 2 years of age. Generally you will get a calf at, say, 6 to 8 months old. You don't want them to be to old if they aren't halter broken. You would get your animal before the tag in for your show is scheduled. Normally you will have had it for a couple months before tag in, though as long as you have an animal to tag in your ok.
Breed is your option. I have allways shown commercial cattle. Commercial animals are generally a mixed breed. At our steer show you don't get to pick the class/category that your animal is entered. You can apply for one, but you have to take your steer to some judges who put him in the class that he best fits. It may not even be his breed at all!
I started with a heifer, but I LOVED steers. This was my baby. His name was Tonka. He was a mixed breed steer out of our pasture.
Both he and I are asleep :)
I'd recomend that you talk to your 4H leader about getting your animals. They can help you find good breeders, help you with any questions you may have about showing. Also if your area has small shows before the "big show" enter in them. It helps to learn showmanship and the in's and out's of the show ring. Mess with your animal EVERYDAY. And I don't mean going out and dumping food in it's bucket. Catch it, rub it all over, get it used to being handled, used to a show stick. Nothing is worse that a crazy calf on show days. Trust me. I was allways recruited to show the crazy ones. NONE of them were mine. Theres alot of work and money that go into raising an animal for show. You have to be willing to put in the effort.