The larger the tank the better IMO, they are terrestial and they don't tend to sit in one place but enjoy moving around to hunt. I'd watch for a 40 gallon breeder tank, which if you watch sales you can get easily for $80 bucks, even cheaper at some expos.

I kept some as a kid in a similiar tank and they did just fine, anything smaller and they get legarthic. They are one of the more active frogs out there.

I would agree with the water situation though, a small dish (changed often) should be just fine. Keep the tank moist. Bag leaves in the fall for a few months to kill any parasites inside and use them as ground cover, those frogs are meant to blend in with leaves and it'll help them feel like home.

I wouldn't worry about winter to much. I keep American Toads and during the winter months they tend to slow down and eat less even with the house at 70-72 degrees. True hiberation never occurs but as far as I can tell they never have seemed to mind it.

Good luck!