Have heard these little trucks make good work trucks.  Need something cheap as a daily driver.  I see some in my area with 4 cyl and auto trans.  Probably not the fastest vehicle on the road, but that dont matter.  Cheap $/mile, low and cheap maintenance and a bed to toss junk in are my priorities.
How are replacement parts cost wise, compared to say toyota?

So your looking at 20 year old trucks. Nissans did not get as good fuel mileage and were not as reliable as the Toyotas. But the Toyotas cracked their frames. And good luck getting parts for these old timers

Your looking at Nissan Hardbody pickups.  Made from Mid 1986 to 1997 Model years. They are excellent vehicles but not without their own quirks.

They also sell for much less than the Toyota pickups of the same era.

I had a 1995 4x4 V6 Auto that I bought with 80K and sold at 225K to a friend. The truck is still running great with 260K on it, original motor/trans. It is however smoking a bit on startup.

I don't know anything about the 4cyl models other that they are reported to be very reliable. I can't imagine how underpowered a 4cyl auto would be. The VG30E V6 I had was only 153HP.

The VG30 likes to shear exhaust manifold bolts but after having mine replaced once at 90K it was never an issue again. Parts were never an issue and they were still building new vehicles in Mexico until 2008.

I would look for a 1994-97 to get the most updated version.

Also aftermarket parts are very limited.  I averaged 18-19 mpg with mine doing a lot of highway driving.

All the basics info is available here: http://en.wikipedia.org/wiki/Nissan_Hardbody_Truck

I had a 91 hardbody many years ago when I was a teen.  It was a good truck but man did it suck gas down.