1. Compute: A Quad core processor. A73 maybe? 2. Storage: 1 Sata Port to host 1 Hard disc. for Boot / Storage. 3. Network: 1 Gigabit Ethernet port. 4. Power: 1 Micro USB port. 5. RAM: 1 GB or optional 2 GB. 3. 1 USB for everything else.
That's it. No Audio port, No HDMI port, No GPIO Port. No Camera port, No extra USB ports. No MicroSD connector. Now considering Raspberry price of $35, I guess board could be done for <$20.
Every few days, I try to find one.