John,
Here is a mini-Raid system for about $75.
Vantec NexStar MX Dual Bay 3.5" SATA to USB 3.0 / eSATA RAID Enclosure - Newegg.com
I do not have this setup. Newegg has a couple of different setups for about the same price. Put "Raid and USB" in the search box.
My setup is for my business and the primary "drive" is Raid 1, but is backed up to another Raid 1 drive every night. The important business files are backed up offsite daily (accounting files) while the server is backed up offsite fully once a week. A little different than your needs.