Bought 2nd hand AppleTV, Privacy? I bought a second hand appletv. My main concern now is my privacy.

Will the person from who I bought it from see what I am doing with it? Will he see when I try to log in using my appleId and see where I live and what I buy?
I'd say it is very unlikely, but if you want to you can do a factory reset which will wipe the device settings, and also download and install the latest system software for your device.

Apple TV (2nd and 3rd generation): Restoring your Apple TV