Looking after a corn snake, what things do i need?

I'm going to be buying a pair of corn snakes. I already have a 4ft viv, with a heat lamp, uv light and heat mats. Does the viv need to include to anything else? Are they best housed on bark? Sand? What temperature does the viv need to be at? Can you turn the lights of at night? How often do you feed them? How much do they cost to maintain. Any info is much appreciated.