You don't need a heat lamp. You need an Under Tank Heater (UTH). Corns use belly heat for digestion. An overhead lamp is not needed for cornsnakes. And with the UTH, it goes on one side of the tank with a hide over it and you will need a thermostat or simple light dimmer switch to control the heat or it could go into the upper 100 degree mark. You will also need a good thermometer to keep an eye on the temps. We use the Acurite digital thermometers/hygrometers (humidity). You can get them and the light dimmer at Lowe's or Home Depot or a place of that nature. Also be sure to put another hide or vines, etc for them to hide in the cooler spots. They pretty much know what they need and when.
Good luck and let us know how it goes!
And pics would be great!
Ask any questions and we will be sure to help you out along your cornsnake ownership journey! And beware...cornsnakes are addicting!! You can't have just one!!!