Welcome Carl!
You're making a risky choice, but one I understand and went the same path myself as a kid with my Big Block Mustang. It sounds like you're pretty "Up" on the Z32 scenario, at least on the surface but be ready to learn a LOT, and be ready to have to do things in ways and at a certain higher level of detail, and perhaps different than you know- the Z32 has it's ways.
As for cost of the car itself, a good solid NA should run about $5-6K depending upon miles and a TT is about $8K-10K same scenario, so a $3,500 NA Z32 is probably a little on the risky side because it will be hard to expect the $1,500 120K maintenance and other things like injectors/harness and cooling system to have been serviced correctly recently given those costs, and the value of the car...basically you will/may have to do those things yourself, and the faster the better if they have not been done and the car used a lot. There will be things to undo and update, and the costs of tires and other things are higher because of the OEM ratings and level of quality of parts used.
As for maintenance I'd say you should easily have $1,500 set aside (same amount as value of car is best actually, up to $5K) for maintenance parts, and be ready for tires/exhaust and perhaps cooling fan assembly, and/or radiator if cooling problems exist. BTW, try to get the least miles on the car possible and less than 150K, and avoid cars with cooling problems as this can be a problem on several levels and by NO MEANS get a JDM motor swapped car (newer JDM import engine into older car) as this is a recipe for disaster.
Focus on the engine first, then drivetrain and then body as your preferences given your cash on hand, planning interior and looks upgrades later so that you get the best CAR to work with, and not a pretty disaster. LOTS of pretty disasters for sale right now all over the nation, not so many solid cars as they aren't being sold for that reason.
Lastly, ask away here with any further questions and by all means do your research, and use the stickies at the top of our page here as there is a LOT of good info there to get started and also deal with your Z32.
Good Luck!
