"I want 2.8mm cameras everywhere to see everything..." - This is why you need specific FOVs with purposeful focal lengths.

Hard to say any more; they multiply like rabbits. Somewhere between 20 and 100 at this point.
Was trying to get an idea of average amount of cameras needed for a well-covered property. Obviously, every property will be different. I have many ideas for camera locations, but they may not always be a good choice. I realize it can take experimentation, but for those experienced, there must be some guidelines to follow that apply to a specific type of area covered - entrance, back yard. driveway, street, etc. Kinda what to do and what to try and avoid.

It would be nice to have a wiki type page as a guideline in a sticky post. ABL - always be learning
 
A lot of how many comes down to the shape of the house and what you need to cover. If you have a 1960s ranch, you're likely going to need less because of the rectangular shape. If you have a newer truss construction home, it will probably be a random shape and you will need to cover more corners and sides. A quick run down of some of my locations is below.
  • Front Door
    • 1 at doorbell height
    • 1 above the door looking down at the porch
    • 1 above the porch looking back the door
    • 1 in the flower bed covering the approach to the door
  • Driveway
    • 1 at the Double Bay header
    • 1 at the Single Bay header
    • 1 at the soffit looking over the driveway
  • Front Gate
    • 1 on the front side
    • 1 on the back side
    • 1 at the back side soffit looking at the gate
  • Deck
    • 1 looking at the stairs
    • 1 looking at the screen door
    • 1 over the deck
    • 1 inside the screened porch
  • General
    • 1 looking at the back gate
    • 1 at the back gate looking at the house
    • Multiple around the house overlooking the yard
    • Multiple in the garage, basement, and specific areas inside the house
 
A lot of how many comes down to the shape of the house and what you need to cover. If you have a 1960s ranch, you're likely going to need less because of the rectangular shape. If you have a newer truss construction home, it will probably be a random shape and you will need to cover more corners and sides. A quick run down of some of my locations is below.
  • Front Door
    • 1 at doorbell height
    • 1 above the door looking down at the porch
    • 1 above the porch looking back the door
    • 1 in the flower bed covering the approach to the door
  • Driveway
    • 1 at the Double Bay header
    • 1 at the Single Bay header
    • 1 at the soffit looking over the driveway
  • Front Gate
    • 1 on the front side
    • 1 on the back side
    • 1 at the back side soffit looking at the gate
  • Deck
    • 1 looking at the stairs
    • 1 looking at the screen door
    • 1 over the deck
    • 1 inside the screened porch
  • General
    • 1 looking at the back gate
    • 1 at the back gate looking at the house
    • Multiple around the house overlooking the yard
    • Multiple in the garage, basement, and specific areas inside the house
please post pictures of your house.