I've had a Z32 NA swapped to TT and loved it. Though trying to not be biased here so I'll offer some input....

As far as mileage I think it was about 20-22mpg on the hwy.

The car can be expensive to maintain. Some of the reason is the lack of room in the engine bay so labor cost goes up if you aren't doing things yourself. The issues most common with Z's are the rear main seal leak, where you have to drop the transmission and replace the gaskets here. So when looking for a Z make sure you ask for maintenance records and look underneath the car. If it has been sitting, make sure that you don't see any oil or coolant spots underneath the car.

Check the suspension and clutch / trans if you are getting an auto. Best advice is to have a mechanic look at it before your purchase

If you are wanting to go with a Z with less $ spent on maintenance for now go with the N/A version as you'll find many of them within your price range. The twin turbo Z's are great and I've had the NA swapped to a TT, made it into a totally different car and that can cost up to $5k in a swap if you aren't doing it yourself. The thing about getting a TT now is there are more things that can go wrong and need maintenance which means more money spent on fixing the car rather than driving.

Best advice is to buy your Z car from an older owner who has all their maintenance records and such so that you know the car was taken care of and to have a thorough look at the car before deciding.