Original Unlocked Apple Iphone 6s Plus Smartphone 5.5" Ios 12.0mp 16/64/128gb Rom 2gb Ram Dual Core A9 4g Lte Used Mobile Phone - Mobile Phones - AliExpress
You should opt for at least a 64GB iPhone 6s if you plan on shooting 4K video
Apple iPhone 6s Specs, Features (Phone Scoop)
Apple iPhone 6 64GB Cell Phones & Smartphones for Sale - eBay