Corn snakes eat mice, (you can buy frozen mice from certain pet shops), there are many ways to defrost the mice, i use a plastic bag in a bowl of hot water, NOT boiling it will cook the feed. I am quite against feeding a corn snake live feed when it will quite happily take pre-killed feed, if you happen to get an awkward feeder then you have no choice but to feed it live prey, which can be dangerous when the corn is an adult as it will be fed adult mice and adult mice will attack the predator as an instinct, so make sure you check with the breeder/shop assistant that it feeds on pre-killed prey. Also ask for feeding records, then you can see if it is a good feeder, i was daft enough not to ask but luckily i have a good feeder.
There are pinkies for young snakes, and fuzzies for slightly older snakes
Older (12 mnths+) corn snakes eat small mice to adult size mice depending on the size of the corn snakes girth. (widest part of body)
(you can occasionally feed you corn snake pre-killed lizards as they would naturally eat lizards in the wild aswell)
As for biting, my corn has never bitten me but sometimes if they are timid they nip, and it tickles apparantly if it's a youngster... and also if they mistake you for food they nip (that's why i use forceps which i got from my local fishing shop), in shed, bad day... there can be numerous reasons for a corn nipping you, but it all depends on the corn snakes personality, you can get placid one and you can get narky ones, that's why i would reccommend you hold the corn snake before buying it.
I would reccommend you shop around for your corn snake as they range from £30-100+
hope you found this information useful