B. M. Bower 
Cow-Country 

Cow Country goes back to some of Bower’s earlier works. Buddy is crossing the Staked Plains with his family and a herd of Longhorn cattle. He is all boy, as were all of Bower’s youngsters whenever they appeared in the various books. He has adventures along the trail but survives them all to reach manhood at age 21, when he is promptly turned out into the world by his father. Well, that sounds a bit harsh. Bud (only his mother can still call him Buddy) is given a choice: ten thousand dollars and life in Europe making music or the gift of a select group of cattle so he can go off somewhere and start his own ranch. (Goodreads)