My family owns property that has MANY trespassers; the property is over 50acres, and on it is a huge abandoned rock-quarry. If I go there I have to kick people out more than 50% of the time and if I don't see anyone I still get to clean up all kinds of garbage they've left behind, but if they are on the other side of the quarry all I can do is yell at them and watch them disappear into the tree-line. So I would like to keep record of the chronic trespassers. Any advice?
If you want to make publication quality images of persons 1000 ft away you are looking at some serious kit, probably more than $20k. Let's assume, though, that you aren't looking to make pretty pictures. Most circumstances I can think of which would require a picture of a previous trespasser involve holding an image up next to the person and saying to them (or the police officer) "Yes, they've been here before." Utility often requires a different approach than beauty.
So with that goal in mind I'm going to recommend a cheaper solution to your problem. A telescope with a SLR mounted via a T-ring adapter will suffer from barrel distortion and radial falloff, especially if it is a full-frame model. You won't really care about this, though, because you will center the face of the person you want to photograph. Check out this resource on astrophotography. If you happen to already own a DSLR and a telscope then this is a very cheap solution for you. If not you can find either item on ebay or Craigslist. For further reading, plug "telescope terrestrial photography" into your search engine to find articles such as this.
Another cost-effective alternative may be a game camera. This is especially useful if there is a known pathway your intruders regularly take. Further, if your trespassers have a favorite parking spot, a properly positioned game camera can capture them and their license plates.
Motion activated intruder-tracking drones are also on their way.
I would check a mirror telephoto. There are some relatively cheap ones.
Here is a review of an 800 mm telephoto and also using a 2X converter.
And here are some extractions from that video. You probably can calculate the distances to the targets using the wider-angle images (using some references like the cars or the street lines) and see if they fit your needs.
Also, take into account that these images are extractions of a video. If you are taking stills you have more pixels to see more information.