Help building a system

I need a 16 camera system that has 3 full 1080p cameras with the rest in either 480p or 720p. I do plan on building the pc from scratch. The client is an 80 year old who needs to be able to use the system so it needs to be somewhat simple and easy to use. He knows how to use eyemax software very well and he would prefer a system with that installed. The most that he wants to spend is a total of $5k for the entire system including the cameras and pc. He also wants to be able to monitor this system from his Iphone or pc at home. Do you guys have any recommendations?