i kept two ball pythons before i got my corn snake, and i now have 6 balls and still one corn.
i think ball pythons qualify as a "starter" snake only for their temperament, and they should be more towards the intermediate side of the difficulty scale: very specific husbandry requirements requiring enclosure modifications or uncommon enclosure types (i.e. not glass), common temperamental eating habits, equipment start-up costs and they are not too active and don't like to be out.
IMO corn snakes are the perfect "starter" snake in all categories: active and out a lot, curious and full of personality, fantastic eaters, super minimal and forgiving husbandry requirements, but they are quick and can be a bit flighty. i would love to add another colubrid, but i don't have the space atm.
FWIW: i don't like the idea of "starter" pets; you shouldn't have to settle on your 20yr commitment because someone says it might be hard. just be prepared and do your research, and be open to help when things aren't working for you. a ball python as a first snake can be tough on both owner and snake (as i know from personal experience), but it is possible to have an incredible and easy first snake experience with a beep.