I don't think the problem is getting a nice one or not, I think it's how you treat your snake and what it percieves you as.
If you get a young snake, it will most of the time hiss, bite, rattle, strike, since it's such a small lil' thing and it can be so easily eaten or hurt by you (in his mind anyway).
However, even through all the teeth and attitude, if you keep handling the lil guy day after day after week after month, it'll learn, "hey, this guy hasn't put a scratch on me no matter how many days I've encountered this guy, and for some reason food only seems to show it's face everytime that guys around". Whenever that clicks into your snake's mind, you've got a tamed animal, though it may still try to get away from you and may not "stay" even after years (they like to explore, they're curious).
But again, I would put that thing as the last problem you'd have, as inherently aggressive corns are few and far between.
Right now I have a super aggressive and very nervous white footed mouse to deal with. I can't even handle her, because she'll suicide jump out of my hands onto the floor, and if I hold any part of her, she'll give me a nasty gash. So what I do is wear gloves and pet her in her cage if she'll let me (she rears up and bites half the time). She's calmed down since, and it's been only a few weeks (and this is a fast learning mouse, and adult mouse, not that snakes learn slow, but they seem to take a bit longer than mice).
If you're real worried about getting an aggressive snake, spend the extra cash and get a full grown and established adult snake. Almost all cornsnakes mellow and and calm down when they get older. Rich Z. has a buncha old snakes for sale sometimes.
-13mur 6
