The post is very vague and misses important things like disk capacity and the type of backup that's already in place. First, even though this has been said before, it's worth repeating: a RAID is not a backup. Secondly, about price, if photography is your business, you need to think about a good backup solution.
(1) External storage: RAIDs are often not necessary, especially since harddrives have reached capacities of 8 TB, although 4 TB drives still offer the best bang for the buck. (Avoid Segate drives, though.) The purpose of a RAID is to ensure storage availability in case of failure or to offer larger contiguous volumes in case your capacity needs exceed that of a single harddrive. The added layer of complexity always adds more points of failure. That's why 2 external harddrives are actually safer as backups than a single RAID1 device.
(2) Sign up for a cloud backup service such as Backblaze or Crashplan. I'm a customer of both, and for $5/month you get unlimited storage for a single computer with Backblaze.
(3) If you really want a RAID, get a Synology NAS: a 2-bay NAS suffices for a simple RAID1 (mirror). There are cheaper alternatives, but Synology is very good with software updates (a NAS is nothing but a computer!), and the hardware is of high quality.