QFA
Thats a bit like saying how long is a piece of string. There are millions of variations, lets start with basic questions:
What sort of facility, office, factory, warehouse, garage,shop?
Budget?
What do you need the CCTV for: Surveillance, Observation, Theft Deterrent, Monitoring with detection, or just to view if something happens.
What sort of quality you need, what sort of area do you need to cover, is there adequate lighting or do you need cameras with onboard lighting.
These are just a few of the basic questions you need to answer before we can even start advising what kit to buy.