a small x86 box with a couple nics and opnsense would work far better.

I go thru the floor but my house is made of wood and drywall.

you need to install samba and setup a share on the linux box first.

this is more suited for r/linux4noobs.

Too old and power hungry at this point. Plus the raid controllers of that generation only support up to 2tb.

Aim for at least a T320 or R320.

Nah, the virtual kvm in the remote management on them doesn't work anymore. Go for a Rx20 series or newer. Those have a html5 based kvm.

you can host on a raspberry pi.

the question shouldn't be can you host, it should be about what you want to host. there's tons of things one can host. see the links in the sidebar of this sub's feed page.

That's a spare PC? I'm jelly.