My question involves labor and employment law for the state of: New Jersey

I was told by a family member that working 2 jobs is illegal. My first job is on an hourly wage and the only time i would be getting paid is if I'm actually there working. The other job is a salary job. I am getting paid a set amount for the whole week. I'm basically just on call all of the time. If i have to go to the second job for whatever reason ill clock out of the first one and go to the second but if i don't have to and I'm just sitting around waiting for a call i want to work at the first one. I was just told that getting a full time salary from one place and sometimes earning money at the second place is illegal. Was hoping people could help me out before i decide to do both at the same time. Thank you.