Just threw this one together. (Just under 900 but I'm sure you and your bud could swap some things around to meet his budget)
PCPartPicker part list:
https://pcpartpicker.com/list/njWcsJ
Price breakdown by merchant: https://pcpartpicker.com/list/njWcsJ/by_merchant/
CPU: AMD - Ryzen 5 1600 3.2GHz 6-Core Processor ($199.99 @ SuperBiiz)
Motherboard: Gigabyte - GA-AB350-GAMING 3 ATX AM4 Motherboard ($93.98 @ Newegg)
Memory: G.Skill - Ripjaws 4 series 8GB (2 x 4GB) DDR4-2400 Memory ($59.92 @ Amazon)
Storage: Western Digital - Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($48.44 @ OutletPC)
Video Card: Asus - Radeon RX 580 8GB ROG STRIX Video Card ($280.98 @ Directron)
Case: NZXT - S340 (Black) ATX Mid Tower Case ($64.98 @ Newegg)
Power Supply: EVGA - 500W 80+ Bronze Certified ATX Power Supply ($36.88 @ OutletPC)
Operating System: Microsoft - Windows 10 Home OEM 64-bit ($89.89 @ OutletPC)
Total: $875.06
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2017-06-25 17:06 EDT-0400