There is no magic count. The right number of cameras comes from what you need to see, not from a package deal. A small office and a warehouse with a loading dock have very different needs.
Too few cameras leaves blind spots exactly where you needed a view. Too many wastes money and buries you in footage. A short walk-through of your space, thinking about what you would actually want to see after an incident, usually makes the right layout obvious.
We are happy to talk it through and point you in the right direction, at no cost.
Talk to a Local Engineer