How does the courts calculate child support for a non custodial parent that does not work?

i have a friend that is skeptical about puting her childrens father on child support because he does not work, he tries to scare her by saying she wont get anything because he does not work. and if she tries he wont give anything, she has to ask him for every little thing they need,sometimes he helps sometimes he doesnt but its always a argument for her .i told her That may have been the case years ago but now i believe they will simulate a income for him based upon his last job.i just wanted some other opinions and professional answers if possible. this is in new jersey