With my Z being almost 30 years old, and poorly maintained, I had a fair amount of work done to the car bring it back to a good standard.
Generally speaking, 260Zs have a tendency to rust if not maintained. Mine was no different with rust in the battery holder, the floor and the tailgate. If you are looking to buy one always get one with as little rust as possible. Reconstructive bodywork is expensive and/or hard work.
The engine and drive train was also quite tired and needed work. Fortunately Datsun ran the a common motor in numerous cars from 1969 till 1983, giving you many options to scavenge parts from.
The radiator and head was an issue with my car. One of the previous owners had put tap water in the coolant system, this resulted in much corrosion of the head. The radiator was also in very poor condition for similar reasons. Both were replaced.
I also replaced the distributor with an electronic one (no points). This made the car run a lot better and is one less thing to worry about when tuning.
The air con was also dead - now removed.
The 260Z is a great looking car and now quite collectible. It has that classic curvaceous shape that never goes out of fashion. Don't be surprised if some people mistake it for a European exotic.
Even today it still remains a quick car, and is also fun to drive with good handling provided by the independant suspension.
Avoid the 3 speed auto though, that slows the Z substantially. I should know as I swapped my car over to 5 speed manual as soon as I could.
Coupes are better looking and harder to find than the 2+2 model. The 2+2 is still a decent car though so don't discount it, the longer wheel base provides some advantages.
The value of Zs is continuing to climb. I've noticed also that the number of wrecked Zs has dropped significantly over the last few years, perhaps indicating that the daily beaters Zs have all been driven into the ground. Rarity can only drive the value up further.