Judith:
I have some Beefmasters in Texas. I do not like messing with bred heifers because I do not know what they are bred to. An 800 pound heifer bred to a 2000 pound bull may have real trouble calving...and if you are not right there with her it could kill both of them. Once a Beefmaster is a cow, she will weigh 1300 or so depending on her frame length and height...she has a lot less problems calving and recovering after she gets milked down. Heifers sometimes have a little harder time recovering, too, because they are not fat and do not have reserves like cows do. This causes missed heats, delayed breeding, and can really have a cow looking peaked for a longer time than you might think. Calves are pushed away from nursing sometimes by heifers just because the heifer herself is having trouble with nourishment. She's thinking, "Hey, I gotta make a living, too--give me a break!" Plus a number of other reasons.
Look real hard at a bull's birth weight and the weights of other calves he throws, and overall thickness before you buy heifers bred to him. On Beefmasters, if a bull is commonly throwing calves over 75 pounds, it is likely he will cause problems with heifers. 65 pounds or so is good for my purposes...I keep the best 1/4, sell the 2nd 1/4 at registered sales, and sell the rest commercial. Anything that won't calve in the pasture either dies or gets sold to the packers. I keep the largest, thickest animals, so my weights here may be a little high for someone looking at Angus. But I want small calves and big weaners (don't read that aloud as it doesn't sound just right)...hell, a newborn calf could weigh five pounds, but if he weighs 700 at the market seven months later, I'll take as many of those as I can find.
I raise (or buy an occasional one) heifers and breed them to my bull at an age and weight I pick to see they have the strength, resources, and body size to calve. I still prefer buying cow pairs after their first calf...you can see what kind of calf they will make which is her whole point of existence. You can see also then if they are going to hang up at calving, prolapse, nurse, etc. If I were you, I would buy young bred cows and expect to buy a bull in a few months after you see the first cow go back into heat after calving. If you buy one before that and put him in with a bunch of bred cows with no prospects of breeding anytime soon, depending on his temperament, he may test your fences.
A young (20-24 months) bull can handle 10 or 15 cows. Pick one that you can walk around without worrying about. A decent registered bull down here right now is cheap--$1500 or so--because of the drought.
Trying to time the AI deal with the time issues I have was lots harder than just buying a bull. The one I have now is kind of a pain because he likes to have his head scratched...concerns me that as he ages he will be pushier and eventually problematic. For now I just shoo him with bucket. feedsack, etc. Later I may have to hotprod him a couple of times to keep his distance. Anyway, adding a bull can be very easy if you really spend some time around them...figure out they are gentle, etc.
I envy you right now. It's like having seen a movie you love and regretting not being able to watch it again for the first time. Starting a herd is like that...wish I could do it again. Be ready for more work, money, and time than you planned on by half, more heartbreak as your best heifer won't breed, the pipes break on Christmas Eve, etc. as I'm sure you have with your horses.
I love cattle...and just when you think you're gonna make a few bucks, you get another bill that makes it break even and you coulda just not done anything. But, then you would've never seen and one all the stuff you seen and done. I will always look forward to calving...maybe this will be the year that old red cow throws a grand champion, you know?