Building a PC for games design? Specs?

Hello, my friend has asked me to build him a PC for games design.

My friend want's to render games in 4K and also do VR, I am not sure what sort of specs to chose, but I have seen some videos and have had a look at some benchmarks, so I thought SLI 1080's but I don't know if this will translate well in real world performance or will just be overkill. Any ideas on specs? open to any ones opinion!