I went the cheap route with this first device.
I bought an IR setup that mounts onto an existing scope. It has a camera fitted to a scope-eyepiece adapter, a monitor screen and an IR illuminator. All of it can be changed from one scope to another so I can change it from rifle to rifle without dedicating any gun specifically to the night vision device.
Since the scope is not moved from rifle to rifle the zero setting of the scope remains the same. I can use it on an air rifle tonight, a .22 rimfire tomorrow night and one of the ARs or a .308 the next.
It also allows me to use the rifle in the daylight as well as in darkness, with or without the IR illumination.
As a pure survival tool it is really appealing. I know that night shooting is illegal but in a survival situation being able to take game at night doubles ones food gathering opportunities, or really triples them due to most game being nocturnal to start with. That is why night hunting is illegal!
When do rats come out? Whenever they think you can not see them, just like the hogs!
I think you will find that rats are available anywhere that harbors a food source. Dairy operations, hog barns and chicken farms are all equally plagued.
When I operated my farm down in Tennessee I made the mistake of lining up the round hay bales in the barn lot so they would be handy for winter feed and easy to shift using the tractor. I had three or four hundred of them filling that barnyard. Those hay bales were rat magnets! The pests dug into them, underneath them and tunneled a small city through them. My cat and dog used to hunt them for sport and leave them lined up on the porch step for my approval. They hunted them as a team with my dog in top of the bales scaring the rats out and the cat cornering and killing them.
So it does not even have to be a big setup that does intense feeding. Just any farm with some grain or hay scattered around and places for the rats to hide and breed.
One female rat can reproduce to multiples that total 23,000 descendants each year and they will live in population congestion that is unimaginable to us.
You might be surprised to discover how many rats you would spot just sitting on your back yard with the lights turned out if you live on the fringe of town.
Now what you need to do is sprinkle some corn around the house, then get up on the roof with your nigh shooting rig and just wait for them to show up.
I got to thinking about how much it costs to hang around here and went back and re-read this whole thread.
Apparently in just 61 posts the forum has spent about $4000, not counting money spent on compressor projects and nifty targets!
We were better off sticking to the ARs.