I successfully ran a modded java minecraft server for me and my friends for years on an ancient thinkstation with a xeon E5430 (quad core 2.6 ghz w/ddr3 ram) doing double duty as a NAS. That old xeon couldn’t carry your i5’s jock on single core performance, which is your main concern. As long as you’re not running huge kitchen sink packs with giant complex bases I think you’ll be fine.
CDs for me. If you buy a big disc binder they really don’t take up that much room. Its about the same size as the 1971 compact OED that sits on the same shelf.
If I really wanted to get rid of them I’d just donate them to the local library system. The ones they don’t want they’d resell as a fundraiser.
Thus forcing everone to wonder why, if they believe some results are fraudelent, they are showing them to us at all.
I expect they will not be worth it as they’re too underpowered for your specific use case. (I’m assuming your use case is hosting complex physical similations for a major university physics department and the old computer you’re considering on Amazon is a used version of this one or something similar.)
For my home server I use whatever old PC I have laying around already.
https://www.freedombox.org/apps/
Whatever you end up doing immediately after you finish setting it up, throw some files on it you don’t care about and practice breaking and reassembling your RAID a few times before you put anything important on it. You want to understand the basic process before things fail.