The most useful systems are more than 4 cameras because they populate the viewing screen software program most efficiently. I currently have a Swann system with cameras installed in the house and around the property. Some of my cameras are at the end of 500 - 700 ft CAT6 siamese underground waterproof cable (TV + power supply). My cameras are 700 line deals and sufficient to tell me what I need to know: who's at the gate, where are the dogs, what's the weather like out there, whose down at the barn and have the guests showed up. My setup is intended to advertise that there is active real-time surveillance 24 hours per day. At night everyone can see the infra-red leds on the cameras that aid in night vision views. I advertise to everyone that comes here so they can tell as well as anyone else that we see them. My DVR controller is connected to my Netgear N wireless router on my U-Verse AP. I keep a laptop dedicated to camera viewing on all the time and can take it anywhere in the house to see the live streams from all the cameras. I also have it patched via HDMI cable to my TV.
I don't believe that I need the extra detail of a more costly digital Ethernet based system because I don't want to string that much ethernet cable at distance limited wireless ranges. Yes you can get repeaters (slowed down data rate) and special antennas (more cost). But you still have to power them regardless. My system cost $349 at Costco and I bought 1 extra camera for a spare. Yes I can view them on the internet, but that's not MY purpose. Other's may want to know in real time who is breaking in when they are 400 miles away but can't stop the damage. I want to know who is here when I am here and I want them to know it when they realize it. My other driveway and field alarms tone up in the house and barn, so the dogs know something's up, I know someone's here, and they know we are all expecting them. Nothing like greeting a 'lost' stranger with the question 'What do you want?' before they get to step out of their vehicle. Even the meter readers know we are watching them. My security system (fences, gates, sensors, cameras, alarm bells and dogs keeps everyone polite and cautious. There's always the Python if the message doesn't get through, but its hard on the wrists and my ears.