if you search the forums you'll find several debates about housing together. Some poeple do it without any problems. The Corn Snake Manual by Kathy Love will also provide tons of information about breeding and housing etc. If housed together, they should be fed separately and kept apart for a bit till feeding response and food scent fades.
Housing together -
Pros: only using 1 cage, heat pad, thermostat, etc. saves $. neat seeing them together in hides or interacting etc.
Cons: STRESS, can not identify which regurge or bad feces belongs to which snake, disease or parasite transmission much more probable - you now have 2 sick snakes, accidental mating of an immature female can have serious health consequences, more?
Breeding - there are signs that will tell you when adult corns (3yrs and suitable size) are ready to breed. Apparently they just need to be introduced for a while and not necessarily housed together. The manual has lots of good information.
The cons seem to outweight the pros in my opinion. Stress can be very subtle and hard to detect but still have serious consequences.
Disclaimer: I am still a newbie myself but read these forums religiously. These are just my opinions. The Corn Snake Manual, and online care sheets and forums (
http://www.cornsnakes.com/forums/ ) are a tremendous help.
Bruce Hatfield