Super Budget uSFF Build

Hi guys-

I'm building a "home server" type computer. This computer's purpose is to run more or less 24/7 and to have all my ext drives plugged into it. It will maintain cloud backups of those drives always, while sharing them on the home network for my primary computer to access them.

I'm aware of the dell optiplex, and it is a possibility but I'm really looking for an uSFF size desktop. Something that is more or less the same size as a MacMini.

I need USB 3.0 ports, ideally 4 or more. Also need 1000Mbps ethernet port.

That is literally all I need. I don't care about it's GPU performance, and in terms of CPU, it really doesn't need to be much. I'm sure an Intel Atom, Celeron probably even a Pentium would be just fine. (provided it is Hackintosh compatible of course) I also will not be dual booting. I will only use this for Hackintosh. I'd like to be able to run High Sierra.

I'm open to buying a used computer, or buying used parts and building one. Open to anything that can accomplish my goal. Looking to spend as little as possible, ideally under 100 bucks.

Any advice?

Thanks everybody.