Hi,
I have both Win10 laptops and Chromebooks.
Chromebooks as said above by Snufkin do what he said, however you can save documents onto a USB stick from the Chromebook.
If he gets a phone contract with a good amount of data, I get 20gig plus free calls and texts for £21 a month and often pair it to my Chromebook, so use it when I go away for a night or two.
Also when it updates itself it does it in seconds not hours like Win10.
You cannot get a virus with a Chromebook.
You can pick up a cheap second hand HP or Acer one for around a £100 and he could use it as a backup to his laptop.
Then he would have the best of both systems.
I use my Chromebook a lot, open the lid and it is ready to go, close lid and it is shut down,very fast to use if in a hurry.
Cheers
John