First, read the Wiki in the blue bar at the top of the page and study the Cliff Notes in there. There's a ton of information that will get you to the point of being able to ask more specific questions that will garner results. The variables, and sheer size, of a system to cover four acres effectively will be challenging and probably require more than a big box NVR style system. Depending on the layout, even Blue Iris may have a problem and you might need professional level VMS systems instead.