First tip, don't listen to pet shops... the advice they give is usually inaccurate and incorrect. If you were to buy a corn snake, the first place I'd go is to a breeder, or to purchase one from a vendor at a local herp show. Pet store reptiles are usually not cared for properly, and 9 times out of 10 you're setting yourself up for large vet bills and heartache in the end.
Before you even get the snake, you definitely want a good reptile vet lined up. If this is your first reptile, and you don't have one already you can find one at
Herp Vet Connection or at the
ARAV Website (Association of Reptilian and Amphibian Veterinarians). I found my vet through both of these sites.
For a baby corn snake, a 10 gallon tank is the best bet to house him in. You'll want the appropriate sized Under Tank Heater (or UTH) to sit beneath the tank. For substrate, paper towels or even reptile carpet is good for that. You'll need to make sure that the substrate temp is in the acceptable range for optimal digestion, which is usually around 85 F. To achieve this, a good thermostat and a digital thermometer with a probe is a good way to monitor and regulate the temps. I got both of these items online from
LLL Reptile. The model thermostat I purchased was the Alife 1000, it's a good little analog thermostat for the price (under $30). As far as lighting, corn snakes are naturally nocturnal, so UVB or supplemental lighting of that kind is not really needed. A light to provide additional heat is okay, so long as you don't overheat it!
Feeding... I'd personally stick to what the snake was raised on and is used to. The corn snake I bought was three months old when I bought him, and was raised on frozen/thawed pinkies. So this is what I continue to find him, if he's fed live, I'd advise you to stick to that. Although I'm not too familiar with what you should do with live feedings, as I have never done this.
Hope all this helps, and good luck with your new friend!
And welcome to the forums