Welcome to the hobby!Ball pythons make the greatest pets and are a perfect starter snakes. I guess most people on here have more than 1 snake as it can be very addicting to collect snakes. For me I am perfectly good with just my one little ball python Crowley, which is now 5 years old. Now this is just my personal opinion but I'd get a hatchling over a grown snake, as long as it's eating F/T before you get it, then raising them up is very easy. I loved to watch my little guy grow up and they grow up so fast, you get to watch them learn to be the snakes they become as adults.
With Crowley I got to see his behavior change slightly over time while he grew, you can tell he had his baby phase, then somewhat of a teenage phase and then adulthood. By this I mean, when he was a baby, he was always in full curious mode and well a little clumsy too. He'd explore every inch of his enclosure pretty much every night and was learning to climb. When he was a baby he'd let his tail slam all the time while climbing down, he woke me up lots during the night making me think he got hurt but was always fine as he could only fall less than a foot. Then came the "teenage" phase, I just call it that as it was after his baby phase and before adulthood. During this time he absolutely loved full body massages. He liked to hang around my neck and warm up there. Once adulthood came he tried to become more independent. He no longer wants help coming out of his tank when it's time to come out and play, he likes to do it himself, I find this just so cute. He also stopped caring for massages though he does enjoy them sometimes. He no longer likes to wrap around my neck as much as he doesn't want to choke me. He got a little tight once and I pulled on him a bit to loosen him up, and like a good snake he did loosen up but it seems that since then he is less of a neck snake, which just makes me think he doesn't want to wrap around my neck because he doesn't want to hurt me. He'll still go around my neck but will keep his tail hanging down rather then wrapping.
Here I am rambling, well I just wanted to share my experience with Crowley and why having him since being a hatchling was such a wonderful experience. Can't wait to see some pictures of your new snakes when you get them and how they are set up.