Hardware noob, what to get?

[dustbunnies]

Relatives asked me to set up more storage for them... I googled and feel that NAS 4 bay would be a good idea. The already have a 2 bay, can I do migration? Or should I still buy 4 new hard disks?

Also, my cousin deals with graphic design and runs application that takes up alot of RAM. He asked me to help him look for a desktop computer that is capable. What should I recommend? Budget wise I don't think he has any.

Thank you so much in advance