Yeah, find out how much money he has to spend.
Read the specs very close and do lots of research. Most dvr cards are 60fps with one carmera and 15fps with four, 7fps with eight etc... and then the numbnuts rarely if ever distinguish between Fields/sec and Frames/sec.
True D1 should be the least to consider, and make sure the camera has that much out... there are a lot that claim D1, but in reality they end up getting out about 240-320 lines.
Cameras vary, but make sure you get one that is sealed and lets you adjust focus and iris and zoom(if you have zoom camera) from outside the case without taking it apart if it is a high mount. If it has to be mounted in harms way, good luck... get it armored with internal adjustments.
For the night vision, most all overstate the range... figure 1/2 to 1/3 what they say. or you could get an accessory illuminator. I ended up going with remote motion sensors and lights as well as night vision. A good camera will start around $250... and the HD can go to $2500.00 each.
The little wireless cheapos on ebay are great for up close and in harm, but really are limited. The best thing I can say for them is they are cheap to replace, and are a decent deterrent. They will be vandalized a lot in bad locations, so you have get creative with your cameras covering each other.
Spider webs, frost, dust, and power outages should be considered, so the system really needs weekly maintenance.
I haven't played with PTZ's at all.