I've done this several different ways over the years.

Ideally, with respect to image quality and delivering a well performing solution, the best way to do this would be with an IP camera that has an on-board HDMI output.

I prefer the Axis line of camera for this setup. You can find a medium-cost 1080p IP camera, which has a fixed lens and also onboard SD Card slot if you need to record at no added cost. The HDMI output is excellent for this exact purpose.

There are other ways to do this as well, such as a less expensive IP camera and a standalone decoder (with HDMI, which can be mounted at/near the monitor and is connected VIA category cable).

The cheapest solution would likely be a simple HD-TVI decoder connected VIA HDMI to a monitor. Run coax and call it day.

I've done all three of the above, just depends on how down & dirty you need to get. Feel free to ping me privately to discuss more if you need bud.

-J