Hello; I'll draft up a quick list of what you'll need for an adult of Corn snake and a rough estimate as to the cost. The prices are assuming you are purchasing everything new. :)
Secure, locking 20-30 gallon long terrarium with screen top- 60-100 dollars
Substrate- 1-15 dollars, depending on what type is used and how much you purchase. Aspen, Paper towels, and Eco-Earth by Zoo-Med are all great choices for this species. Avoid anything containing Pine or Cedar; as the oils in them can be toxic to small animals (reptiles included.)
Two thermometers and a hygrometer- 5-20 dollars, depending on the quality and type used.
Heating apparatus of some sort (Heat lamp, ceramic heat emitter, under-tank heater)- 20-30 dollars.
Two or three hides- 10-40 dollars, depending on which variety you choose. Try putting one at the hot end of the tank, one at the cool end, and if you have a third; one in the middle that way your snake never has to choose between proper thermoregulation and feeling secure. :)
Water dish- 1-15 dollars, depending on type used.
Unnecessary, but still nice to have Corn snakes:
Cage decor, such as branches, fixed rock formations, or decorative plants made for reptile use not only improve the look of the terrarium but also give the snake something to rub against while shedding- 5-60 dollars, depending on where it is purchased, how much, and what kind you use.
As far as other reptiles go; Here is a list of my top 10 favorite snakes that are great for beginner and experienced snake keepers alike (Corn snakes included); along with why I chose them, and a care sheet on each species. :)
1. Rosy boa. They are small, very docile, calm, are great eaters, and are slow moving (and thus easier to handle than a lot of colubrids like King snakes and Corn snakes). They are also very hardy, low maintenance, come in lots of different colors and localities, and aren't prone to shedding problems.
Care sheet: http://www.rosyboa.com/desertboas/caresheet.html
2. Kenyan sand boa. They have all of the good qualities of the Rosy like the gentle disposition, ease of care, small size, great feeders, etc, but the only problem that some keepers may have with them is that they spend most of their time under their substrate. For those who like to randomly walk by their snake's cage to check to see what the snake is up to and how it is doing, that could be frustrating for them.
Care sheet: http://www.wnyherp.org/care-sheets/snakes/kenyan-sand-boa.php
3. Corn snake. They are quite docile, low maintenance, great eaters, generally are great shedders, are a bit bigger than Rosys or Kenyans but not so big that they are awkward to handle, and come in a wide variety of colors. My only thing I'd worry about for a beginner with these guys is they are very quick moving and can be quite nervous as babies, so they require a bit more caution when handling.
Care sheet: http://www.anapsid.org/corn.html
4. Childrens pythons. They are very small (the second smallest python species in the world), are low maintenance, are great eaters, and usually have a great temperament. While I wouldn’t classify them as slow moving, they aren’t all that fast, either. However while I think that they are quite beautiful; some would consider them to be ‘bland’ looking, so if one was in search of a flashy looking snake, then these guys probably wouldn’t be for them.
Care sheet: http://www.tinypythons.com/caresheet_childreni.asp
5 & 6. King snakes and Milk snakes. I lump both species together due to their similar appearances, temperaments and care needs. The only notable difference in their behavior is that Kings tend to be a bit quicker to settle down when being handled. Both are a bit bigger than Rosys, Kenyans, or Childrens (roughly the same size as a Corn, though may be bigger or smaller depending on the subspecies), are low maintenance, great feeders, and usually tame down quickly with regular handling. The problems with these guys are that they are another quick-moving species that tend to be nervous when young. They are also cannibalistic, so it is under no circumstances a good idea to put a Milk or a King in the cage with another snake if you wish to keep both snakes alive and well.
Care sheet (works for both species): http://www.kingsnake.com/rockymountain/RMHPages/RMHkingsand.htm
7. Rough-scaled sand boa. These guys are a very small, generally docile, low maintenance species of sand boa. They are hardy and easy to care for, are great feeders, and are excellent for beginners. The only problems with these guys is that they are a bit harder to find than most of the others on this list, and like the Kenyans, they spend most of their time buried under their substrate.
Care Sheet: http://www.reptilia.org/care_sheets/snakes/csheets_snk_rough.htm
8. Ball pythons. They are a normally very sweet-tempered, medium-sized species of snake that is quite popular with beginners. They are slow moving, beautiful and exotic looking, easy to handle, and reluctant to bite. Unfortunately due to their high humidity needs, shedding problems, and notorious issues with feeding, I would only recommend them to a beginner if they had done extensive research on their care and knew how to deal with the common problems that they may have with these guys. Better yet if they had a ‘coach’ of some sort, another Ball python owner who knew how to handle this species, and could tell you the best kind of caging for them, the best sorts of substrate, and what to do when the snake goes off of feed. If the person knew how to deal with those issues, then these guys make a wonderful beginners species.
Care sheet: http://www.anapsid.org/ball.html
9. Hog Island Boa. These are a very beautiful, generally docile species that are medium sized and medium upkeep. They require a bit less humidity than other subspecies of Boa Constrictor, and are usually fantastic feeders. The only problem with Hog islands is that they are a bit difficult to find.
Care sheet: http://www.centralpets.com/animals/reptiles/snakes/snk2756.html
10. Western Hognose Snakes. They are a usually good-tempered, low maintenance, small, amusing species that could be mistaken for a Rattlesnake if someone wasn’t well versed in reptiles. They are generally very sweet, tame down quickly, are great feeders, and are great shedders. They are mildly venomous, though not enough so that it could pose of any danger to humans. Not only are they reluctant to bite; their fangs are also located in the back of their mouth thus making it very hard for them to bite you unless you literally stick your finger in there. Even if they did manage to bite you; you’d have to let them ‘chew’ on you to get any sort of reaction at all. Generally the reaction from their venom in humans is mild irritation and swelling.
Care sheet: http://www.reptileallsorts.com/westhognose-cs.htm
If you are interested in lizards; have you considered a Leopard Gecko, a Crested Gecko, a Viper Gecko, a Gargoyle Gecko, or an African Fat-tailed Gecko?
All are small, nocturnal so they don't need UV lighting, low maintenance, docile, interesting looking, hardy, do quite well with handling, and I am not sure how much prior reptile experience you have; but the African Fat-tails, Vipers and the Leopards in particular make great starter lizards. :)
Here are care sheets for all of the Gecko species I just named:
Leopard Gecko:
http://www.thegeckospot.com/shortleocare.html
Crested Gecko:
http://www.pangeareptile.com/id52.htm
Viper Gecko:
http://www.acmecritters.com/CARE_SHEETS.html
Gargoyle Gecko:
http://www.pangeareptile.com/gargoylecare.htm
African Fat-tailed Gecko:
http://www.acmecritters.com/CARE_SHEETS.html
I hope this helps, and if you have any further questions at all on the subject or on any of the species I named; please feel free to message me and I will be more than happy to assist you. :)
Good luck!