tl;dr: Get Synology.
It depends what you want to back up, how much money you want to yank out, and what inconvenience you're willing to take.
Everything not-source is pretty much scratch data anyway, complete OS is restored from a DVD image when necessary.
Sources (i.e. your source repository) are best in a revision control system anyway which is a "kind of" backup in itself, though obviously you should have a reliable backup of the repo, too. I've done that with a subversion server on a linux box in the past, and running on a cheapish NAS all with self-made bash scripts for daily backups. Total shit.
In particular the latter (a cheapish WD NAS) turned out a nightmare in retrospective. Nightmare as in total data loss (good job the backup script worked, heh).
So this week, I got my Synology 4-bay station delivered, and it's just awesome. Plug in some disks and it makes them RAID with redundancy and with no questions asked, and no trouble. RAID is no backup and no replacement for backup, but it is one step in that direction already.
Besides the obvious (working as network share), diskstation is one click to have a Subversion (or Git) server running. One click to have it back up automatically to a second diskstation or another network share (or cloud), if you wish to have that done. Oh, and it's 100+ MiB/s read and write on the average, and it comes with software that manages our security cameras as well with no extra computer necessary...
The price tag is steep, but it's worth every cent in my opinion. Just buy two of these, one for hosting the repo, and another for backup.
For backing up "normal stuff" on a desktop computer (non-programmer) I can recommend Seagate replica drives. Totally unsuitable for a programmer's machine since the software is too intrusive, but for the average user (such as your wife) it's just great. Plug it in, and do not think about it any more. Backs up everything secretly without you doing anything, and even lets you browse file revisions if need be.
