getting email and messages on ipad by several different people

i have an ipad and would like for a friend to use it. he wants to be able to get his email and messages on the ipad.

seems it will not let him do that as an extra email address on the ipad - i am told error... already in use (since it is already in use by him on his iphone.)

we want our messages and emails to remain private for each of us.

can this be accomplished?