I'm not sure about where you are from but in my area grass fed beef is huge! You can make a lot more money that way even though growth is sometimes slowed a bit. Don't try to do it unless you are going to make sure not to overstock your pasture or you have excellent quality hay to supplement with.
If you're planning on getting newly weaned calves they should be given grain for a couple of months... their rumens aren't functioning efficiently enough to digest strictly hay although they would do well on quality grass. It's not like horses either..you want to make sure they have access to feed at all times. The more they eat the faster they grow.
Vaccinations in your area may be different as well but we vaccinate for respiratory disease and BVD (using Bovishield Gold) pinkeye and rabies. You probably won't need to deworm because they will be slaughtered at a fairly young age and won't have time to develop a large parasite burden. If you notice that they are not gaining you can deworm them... We deworm our dairy cattle once a year with a pour on solution (Eprinex).
As far as breeds I love herefords! I don't have any experience with Angus but I like the idea of them too. Don't fall for getting a beef breed crossed with a dairy breed..it's really not worth it. Dairy cattle are not meant to have a lot of meat on them so a cross is less than ideal although they are cheaper to purchase. Also, it pays to ask the farmer you're buying them from to dehorn and castrate them if you want that done because they are simple procedures for most farmers to do and it will save you quite a bit of money by not having to pay to have a vet do it.
And the best part about having cattle is you get to chase them with your horse ;) Have fun with your new bovine hobby!