Well, here is some thoughts
Cameras:
Outdoor case;
Operating temperature: -30...+30;
1/3 inch CCD(IMHO 1/4 inch is too small, bad quality of image);
Horizontal resolution 400-500 tvl.
DVR:
4 channel will be enough;
without pre-installed HDD preferable, I have a few disks and I can install HDD by myself.
I'm also have cat. 5e Ethernet cable, but I don't have power supply for cameras. Cameras will be installed at the height of 2,5 meters on the wall of the building. What do you think about cheap chinese 50...150$ DVRs that widely available on eBay:
http://www.ebay.com/itm/330565584487
http://www.ebay.com/itm/220761639276