It should give power to them, and give a SATA connection to them. Roughly so:
...except that I want to put 3.5'' SATA drives in it.
What I want, externally: simple SATA slots, connected to the drives directly. All "intelligent" solutions, particularly complex NAS servers, etc. are all big no-no. I only want a physical storage for the hard disks, the NAS part is done by me.
Nice to have, but not a requirement, if at least some of the HDDs can be hot-swapped (removed without screws).
Price should be consequent to the near-zero electronics. (Obviously it should be cheaper than a NAS.)