Well, before you even consider buying a corn I recommend that you buy the Corn Snake Manual by Bill and Kathy Love. This book, in my opinion, is the bible of corn snake keepers.
To answer your questions:
- Well, I don't have a clue about gallons but a baby corn should be housed in a viv measuring about 1.5 feet by about 8 inches. A long time before they are fully grown, they should be in a viv measuring between three and four feet with a depth of about 18 inches or so.
-Corns have lots of teeth that face inwards, which hold prey in place as the snake constricts. Baby corn bites don't really hurt at all because they are so small but an adult bite can sometimes be quite a shock. All bites should be treated with an antiseptic cream. Corns are generally good-natured snakes and only really bite when provoked. However, you do get the occasional little bugger.
-The best food for corns, both in captivity and in the wild are rodents ie. mice. Baby corns eat 'pinky' mice (babies with no fur) and adults eat adult mice. The stages in between are 'hopper' and 'weanling'.
-A good tank will cost about £75 or $100 but you can probably find them a bit cheaper or buy a second-hand one for $50 or so. Other vital items are -heat mat -substrate -two hides -thermostat. I'm not sure how much these cost if you're in the US but when I first started out I spent £200 on the whole set-up including the snakes. If you shop around you will be able to beat that price but the keeping of snakes ISN'T CHEAP. Climbing branches aren't necessary and can take up a lot of space. However, some corns do like to climb so there's no harm in providing one- just make sure it's securely fastened.
-Corns are among the most easy snakes to care for but they still require lots of attention, time and money and they don't like being messed around.
-Corns, on average, like to be handled but not 'played with'. Reptiles aren't the sorts of pets you buy for a cuddly relationship. With regular handling, your pet should become quite tame but will not sit quietly in your arms or around your neck. Corns are very lively and just keep on moving.
Hope I was of help and, any time you have a question, just post it and someone will help you out. Remember what I said about the Corn Snake Manual -Read it!!!!