>>I would keep it outside in the summer and let it hybernate in the winter. I live in Nevada.
NV seems pretty low-humidity for an eastern's liking. If you're set on boxes, a T. o. luteola would be the closest-ranging to your location so therefore would theoretically be most suited to your climate. Even so, providing an area of damp soil for a higher-humidity microhabitat (where the turtle could burrow) would help.
Have you looked into adopting a desert tortoise? I can't remember the name of the organization which handles them, but it might be tough to get approved given your current experience level. At least they're native to your area, and if you have sufficient space in your yard your primary upkeep concerns would be reduced to provision of food.
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Chris McMartin
www.mcmartinville.com
I'm Not a Herpetologist, but I Play One on the Internet