How do you provide bucking bulls to rodeos?

I know being a stock contractor is the answer but i have been helping out my friend who has a couple of young bull calves and we want to take it a step further and raise them as bucking bulls... when i say a couple i mean like three and no more.. I know we first have to see if they are real bucking material but how do we go about getting these bulls, when matured, entered into rodeos?