I'm not the OP but I use a 2008 Mac Pro: https://everymac.com/systems/apple/mac_pro/specs/mac-pro-eig... 8 cores, 32GB of RAM, 4 SATA drive slots - found it used for only $400 CAD.

A 2010 or newer Mac Pro would allow you to run the latest macOS version.

Mac Pro 3.1 from 2008 with 2 quad core Xeons at 2,8. You can get one of these very cheap (300 euro maybe if you buy the memory separately). As the other poster says, the only drawback is SATA2 disks speed.