where are you located? Do you live in the southwest united states? If you keep the desert tort you will want to house her/him outside and North American desert torts live in the sonora and mojave deserts, very warm dry places. Raising gopherus in different climates can be very difficult. If you do live in the Southwest US you will want to check with the legal situation as they are protected everywhere to differeing degrees. The American desert tortoise has VERY specific dietary requirements and they can be difficult to feed properly if you don't know where to get the right things.
The websites katrina mentioned are excellent but you may want to look here as well:
desert tortoises at WCT
There is not an abundance of good info on graptemys (map turtles)or their care in captivity on the webI if you want general advice about the map feel free to email me privately; i have a bunch of maps and would be happy to help.