buying a car that isn't registered
 

I'm looking at a used car that has not been registered/insured in the past year.
The guy I'm buying from bought the car a year ago and never bothered to register it.

What will I need to register this car in NJ other than the title?
Will I have to pay any fines because the car wasn't registered/insured for a year?

It varies significantly state to state. In most states you need a completed bill of sale, proof of insurance, and title. Some require you to also have it inspected prior to registration. I've bought vehicles in similar circumstances, usually it's just a 10$ fine for late registration.

It's best to go to your local DMV and ask; more accurate than asking on here. ;)

I am not a lawyer, but I play one on the internets. Yes contact your local DMV and get the list of hoops you will need to jump through to register the car in your name.