I doubt anyone who is too tight on cash that they have to think about the electricity cost of a home server can afford a Mac.

Only thing is you can't run Proxmox which makes self hosting much better, and you'll be limited to ARM builds, which on server is at least a lot easier than trying to run desktop apps. Modern micro desktops are also fairly power efficient, perhaps not quite as low as the mac, but much lower than a regular gaming desktop idling.

Avoid stacking in too many hard drives since each one uses almost as much power as the desktop does at idle.