I bought a cheap used Dell R710 on Facebook marketplace for like $100 or so, as well as an ups, rack, 10g switch, etc, from various other sellers. All told, I’ve got about $500 in my server setup.
Installed proxmox on it. It’s “free” if you don’t buy a license. You just have to put up with a little nag screen when you open the control panel but it still works 100%, much like winrar.
Edit: just realized this is in c/selfhosted AND I misunderstood the post. I’m gonna leave it here just on the off chance it’s useful to somebody, but I acknowledge it’s not what you’re looking for.