The amount of Ring security cameras you'll need depends on your space. If you are in a smaller apartment, and just want to keep an eye out on your front door, one doorbell camera should be enough protection. If you are in a bigger home with more entry points, one or two outdoor cameras to monitor each entry point should be enough.  If you want to keep an eye on the inside of your house to watch over your kids while they're with a babysitter, or just to check in on your pets or valuables, you'll want at least one indoor camera in each room you want to monitor.