They are great fun cars, I highly recommend them. The three biggest problems with the first-generation Z-cars are, in order of severity, 1) rust; 2) rust; and 3) rust. (This from an east-coaster who's made more than one trip to your side of the country for an early Z.) Long ago, there was a joke about early Japanese cars .. if you scratch the paint, you can just about make out the Budweiser label.
Check out the frame rails (C-channel steel from the radiator support back), the floor pans (specifically the area behind the front seats -- rip up the carpeting!), the rocker panels (I had a '75 Z and a '70 K5 with matching cancerous rockers!), the rear wheel arches, beneath the battery tray, and the finishing panel around the hatchback latch. If it's structurally sound, just about anything else is a fairly easy fix.
The L28 engine is just about bulletproof, but make sure the engine accelerates, decelerates, and idles smoothly .. otherwise, you may end up learning more than you'd ever cared to about the early Bosch L-Jetronic fuel injection system and how it interfaces with Datsun's air-flow meter, cylinder head temperature sensor, and cold start injector.
Listen for the trademark "clunk" from the differential on brief on-throttle/off-throttle maneuvers (indicative of a worn mount and/or missing relief strap) and for a noisy throwout bearing.
The gauges are usually reliable though not necessarily accurate, and the clock won't work. /forums/images/graemlins/smile.gif HVAC is decent. Weatherstripping is usually sub-par after 25 years. There's a plethora of hi-po upgrades available.
Feel free to contact me via PM or email with any questions. Good luck to you and your friend.