Range is $10,000 - $15,000
Question which do you think are a better more reliable one C3 or C4?
Now.... The C3 is classic. No doubt. The C4 is a great Corvette as well but you need to be careful buying either. A good C3 will likely be over your price range unless you are mechanically inclined and want a project car. The major issue to watch for in a C3 is the frame and birdcage condition. the birdcage is the cockpit frame assembly and is famous for rust rot. You can't see this unless you remove the kick panels around your feet. Frame condition is a little easier to check by getting the car on a hoist and should be looked at whether it's a C3 or C4. Avoid either one if it looks like it hasn't been maintained properly: caked oil in the engine compartment or the undercarriage, twist ties holding wires and hoses everywhere, etc.
If it were me buying a C4 (and I will likely catch some flak for this), I would hold out for the later years (1989 on). The early C4's had a few more issues. The 5.7 crossfire in 84 was a bit of a dog with only 205 hp and had some other problems along the way. The Doug Nash 4+3 tranny also has been known to be problematic. Not slamming any of these for the guys that own them. Just putting it out there.
Again. Unless you want a project car, avoid the car that has been sitting outside or in a field somewhere for a long time. Look any car over extremely well, write down the Vin number and do a carfax history report check on it. And when you think you have found the right car, pay the piper and have a mechanic go over the car with a fine tooth comb before you ink the deal. It will pay in the end. It it extremely easy to spend another $10,000 fixing problems if you buy without paying attention.
If you think you have found your car, I would recommend posting again in the C3 or C4 section of the forum, give us details, and get some more feedback on your prospective choice.
Now I will let some members with more experience with these models than me chime in.