There are many ways to accomplish what you are asking. Choosing which way is best for you would take much more info. I will lay out some of the basics and see if you want to give more input from there.
1) Completely segregated network with it's own switches, router, internet connection, etc.
Under this style of network, the camera LAN would only be accessible by the corporate LAN via an internet connection.
2) Physically segregated network, but sharing a router.
Under this scenario, the camera LAN would still have it's own switches, but would be using an alternate port on a shared router. Under this scenario, you could provide access through the router from the corporate LAN to the camera LAN, if desired. This could be restricted to the bare essential ports and protocols, enhancing security.
3) Physically segregated, but using multiple network cards in your server/NVR
Under this scenario, your recording device, whether it's a VMS server or a dedicated NVR, will need to have multiple network interfaces; one facing the camera LAN and one facing the corporate LAN.
(Matt Ion's way of using one NIC isn't the same as this scenario. Under his one NIC scenario, nothing is segregated, physically or logically.)
4) Virtually segregating the networks via VLANs.
Under this scenario, you would have the camera and corporate LANs on the same switches and router, but configured as virtual LANs (VLANs), which means each LAN would be segregated by use of switch and router configuration.
Now, deciding which is best for you is the hard part. If your client has managed switches, a robust router, and an adept IT dept, then option 3 is the most practical. But, if they don't have any of these requirements, option 1 will be your only choice, unless you add a better router ahead of the existing router.
There are no absolute rights an wrongs here. Every option has it's time and place. There are cost and security trade-offs with each option. Knowing your customer well is the first step to choosing the correct option.
I would highly recommend taking the next IPVM networking class.