Cheapest cpu+mobo combo for 4 gpu rig?

[Aquazi]

I got my hands on 4 cheap 470s (used).

I want to build a 4 gpu rig, but I'm interested into the cheapest option.

I'm often confused about which motherboards are better for multi gpu.

I'm not interested in those BTC boards (they are rather cheap tho), but I'd like to cut the expenses even more.

Any good recommendation?

I could even try to look for some used motherboards+cpu combinations but I don't exactly now which specs I need to check on producers page (I get confused with all the pci, pci-e, ecc specifications).

[whitrzac]

With 4 cards you pretty much just need a board with 4 pcie slots. Nothing special.

You could probably pick up something off fleebay for $50 that would work.