I have a Dell R720XD as my home NAS. I bought it used off eBay. The XD version has 12x 3.5" drive bays. I have eight of them occupied with 8TB spinning disks. The server runs TrueNAS and the disks are part of a ZFS RAID. I spent a few hundred dollars on the server itself, a hundred or so on more RAM, and $2200 on the hard drives.