What KVX was trying to emphasize was that Hognoses like to eat toads, and only toads. Toads may be very difficult to find and obtain as a food source if you happen to own a hognose, or catch one.
Snakes can be alot of work, depending on how much you know. I suggest you read up on the care of Black rats, Garters, and Greens BEFORE you go out and catch one. Make sure you have everything set up and ready to go, do not catch the snake and then go to the petstore to buy all the supplies. Just get the basic setup: a 15-20 gal tank w/ an escape proof lid (I recommend 30-40 gal tank for a black rat, those are very expensive tanks), under tank heater, water bow (can use a crock pot), a couple hides (can use cardboard boxes), something to climb, and use paper towel as bedding, and get a good digital thermometer from radioshack. You will probably end up spending about $50 on the supplies.
Also, when you say "outside in a heated/cooled building" I take it you're meaning the garage. Though some people keep their snakes there due to family matters, I suggest you keep it in the house where the temps are more controllable. If you can't get your mom to keep a snake in the house, then think of what that might mean if you were to get that cornsnake you wanted. If your mom is THAT unwilling for you to have a snake in the first place, going out and proving that you can care for a snake won't change her attitude toward them. You have to educate her.
Also, the vet visit is mandatory if you plan to keep a wild snake, or even captive bred for that matter. Some people might get lucky and have a seemingly healthy snake that lives for years, but sometimes you won't be as lucky as those few individuals and end up with a dead snake, or you yourself get sick. This bit of advice should be heeded at all costs, almost all snakes in the wild carry some sort of parasite or another, see this page:
http://www.exoticpetvet.net/reptile/zoonoses.html
So if you get worms from your snake, you need surgery to get them removed (who knows, you can be the lucky, or unlucky kid to catch a snake with a rare pentastomid worm that's transmissible to humans, and they can litterally eat your liver out). Also, ask around where you live to find a good herp vet, try your best to find a good one, your snake, and all future snakes you may have may depend upon that vet.
And yes you are correct, there are no species of protected gartersnake in Ohio, HOWEVER, the lake erie water snake and the timber rattler ARE protected. The lake erie water snake can easily be confused with a black rat due to their size and colouration. Be absolutely certain of your identification of the snakes you catch.
Instead of catching a snake, why not save up to buy a garter or green at your local petstore? They're fairly cheap, usually no more than $20 and most often around $10. Though I'm against lying, you can tell your mom you caught it if you have to. It'll be safer (hopefully they're not WC), and easier to acquire.
Also, good luck catching anything in this weather, you'll be lucky to find anything that even remotely resembles a snake. Means you have alot of time to plan, try early April on warm days, the snakes should come out of hibernation by the masses. Stay away from wooded areas and black rats for the good part of spring, they hibernate with venomous species and are always found with them early spring when they come out of hibernation, that's why they're called "Pilot snakes". Get an old golf club (makes a good snake stick), and a good sturdy burlap bag, and don't forget the adult, they're really important tools (like when you need some money to get an icecream from the icecream truck)
Look along open fields and grassy areas, I really think you'd do much better with an eastern milk than any of the snakes you stated. Easy to catch as well. Good priming snake for a future cornsnake keeper. Did I mention, they're much prettier than black rats or garters?
-13mur 6