By the way if you're on linux btrfs has self healing capabilities (and any of the cheap 2/4 bay 64bit synology nas can use the btrfs self healing and coupled with raid protect your data from rot). Not a very big expense for a lot of safety.
Think a NAS will be a future investment.
As the other commenter said you can also built it yourself but frankly configuring Samba and its permissions and updating your mdadm config when changing a drive and all the other things gets boring and borderline dangerous really quick, just know that if you buy a pre-made NAS what you're paying is not really the hardware (you can get better for cheaper if homemade), it's the software.
I like DSM (synology's software) because it doesn't get in your way, it lets anyone use easily yet still offers the advanced options. If you've never had a NAS or don't want to spend hours in config files every now and then, I recommend it.
(as usual the question for devices like this is not so much "how easy is it to set up" but "how easy it to recover if say a drive died and you need to repair your array")