Looking for a refurbished or new iMac for my dad.

[Lost-in-FL]

What ya'll think? He is 79 and have problems with his vision. The reason that I want to get an iMac is really for him to read ebooks because he is no longer able to read books or the newspaper for long and
all e-readers I have seen seem too small (even with the letters maxed out) for him. Because he worked all of his life in construction he is getting depressed because he is no longer able to work. Now that is having difficulty reading it is getting worse and knowing this is breaking my heart. He has NEVER used a computer in his life beside a calculator. Macs are easy to learn and my nephews are open to teach their grandpa on how to use it. I picked iMac instead of a laptop because I want something that he can magnify to the max so he has to make little to no effort reading. I will be the nook for mac to download his favorite books. I like the iMac because of the large screen but I am debating if to buy a new or used iMac. Any suggestions? Do you know of a place where I can get refurbished iMacs besides the Apple Store? Should I go with the previous model (the all white)?