You live in hellsville when it comes to child support. As long as your adult child goes to college, you can pay as late as their 23rd birthday. It doesn't matter if they live on campus. Support continues to the custodial parent so they can maintain a bedroom for them if they stop by.
I read a case a few years back where a child, going to college, moved to the former NCP's home. They were able to get CS stopped, but could not collect. Later, the adult child moved back into the former CP's home....and they were able to get CS reinstated. Case law therefore is that whoever is the CP before the child's 18th birthday is locked into that status regarding CS.
NJ also likes to force college and living expenses upon both parents, although the higher earner is going to pay more.
“There are those that look at things the way they are, and ask why? I dream of things that never were, and ask why not?”