I have a friend who has a tv with cable, but no internet access, if I buy an Apple TV will it still work for him?
Depending on your use an ATV does not require an internet connection to work although it does need a WiFi or Ethernet connection to your home network to AirPlay or stream media. Obviously you need an internet connection to view online content such as Netfix, Hulu and so on. But no internet connection is needed to view media stored on iOS devices or from iTunes on a computer, just a connection to your home network.
You will only need an internet connection if you want to use it for any purchased media through iTunes or if you had previously purchased any iTunes content, then it would occasionally require internet access to authorize those purchases.
Hope this help provides you with the info you need to make your decision.