300zx's are not reliable, no car with that many miles tends to be, unless its a 4 cylinder honda/toyota
A "sports car" with that many miles with an already complex motor...your looking for issues, and its only going to become more expensive with a "newer" car. Im in college as well man but already work full time. I say your best bet is, get a mid 90's saturn like I have, you can get them for like 500-1000 dollars, there cheap, reliable (if you respect them) and get 30mpg. Get a side job and start saving your money, find the car you want, dont settle. Wait till you know what you want to do as well. Guys can change there mind 10 times over during a build, and it can cost you a lot of $$$ Figure out what you want to do with the car. Price it out, add 5 grand, and do it!