alt Hacker NewsTape drives are generally SAS so you will need a controller card
I've got a HP StorageWorks Ultrium 3000 drive (It's LTO-5 format) connected to one (LSI SAS SAS9300-4i), in my NAS/file server (HP Z420 workstation chassis). Don't go lower than LTO-5 as you will want LTFS support.
About £150 all in for the card and drive (including SFF-8643 to SFF-8482 cables etc..) on EBay
Tapes are 1.5TB uncompressed, and about £10/each on Ebay, you'll also want to pick up a cleaning cartridge.
I use this and RDX (1TB cartridges are 2-4 times the price, but drives are a lot cheaper, and SATA/USB3, and you can use them like a disk) for offline backup of stuff at home.
Not OP, but similar situation, trying to figure out tape archiving, already using SAS.
However, is there no open formats? The whole LTO ecosystem of course reeks of enterprise, and I'd expect by now at least one hardware hacker had picked together some off-the-shelf components to build something that is magnitude cheaper to acquire, maintain and upgrade.