I got a HP 1200w sever PSU and 12 GPU breakout board. It came with all the cables needed.

I use the Server PSU to power all the GPUs and Risers. I use a Corsair 500w to power the motherboard, CPU and SSD.

I power up the Server GPU first then the motherboard. If you are worried about the system going down while you aren't not home, you can also set up on Wifi Smart Plugs so you can manual turn off and on while away from Rig.