First and foremost is this a one story house? Two story? What does the access look like in your attic ? Are there any vaulted ceilings that block access ? What areas are your greatest concern? If I was installing the system I would recommend one covering the front door/ front porch area, second one would cover the driveway , third one in the screened porch in the rear. Without know what your landscaping looks like it would be difficult to suggest other locations, when I inspect a customers house I walk the property to see if there are trees, shrubs etc that may block a cameras view, than I will gain access to insure that I can route the cable to the camera locations and the NVR. There are many things to consider when planning a security camera system, and I will be more than happy to help if I can. What type of system are you looking to install? Analog, IP or HD-TVI? Is this something that you are looking at doing yourself or are you looking to hire a company to do the dirty work.