I like and use the WD MYCLOUD home NAS unit it is easy to use and you can setup separate folders (shares) for each computer. I have the 4TB unit and have 4 different machines using it. One of the things I like about it is you can expand the base if 4TB is not enough just plug in a WD external hard drive into the MYCLOUD and expand your capacity, I am thinking about adding a 6TB unit to my 4TB base.

Others have stated that you will also need a offsite copy and I agree, I just disagree on how to get it there. What I do is the most critical data is written to another external drive (locally) and that drive is stored offsite (repeated as necessary). If your storage requirements are low cloud works and can scale for you. In my case I do not want to think how long it would take to get 4TB into the cloud and back out. Or how much that might cost, in my case the scale that concerns me is bandwidth.