theoretically any HDD will work on a NAS, with a redundancy setup it would secure the files from sudden failures, although their durability will decide how often you'd replace the HDDs.
try setting up a nas using hdds that have fast head parking, guarantee you'll throw it in the bin within 6 months (with moderate usage). Also, you'll want a drive with some sort of ERC (like wd's tler) if your using raid, or again you'll be up shitcreek in not time.
Btw, just get a straight external, it wont be cheaper getting your own enclosure (due to the flood + contracts, asshole companies keeping capacity permanently lowered, etc).
And why the hate on "green" (5400) drives? You'll be using it as an external, unless you've got native usb3 (no those nec, or any thrid party controller dont count), esata or thunderbolt the link will be saturated long before a 5400rpm drive is at its max.
Also, externals are really only designed to be used lightly as a backup solution or a large portable storage, it'd be best to go with an internal if its going to recieve a hammering.