In NJ it is standard practice for the SELLER to be responsible for obtaining the municipal certifications including the "smoke cert" (smoke detectors, CO2 detectors, fire extinguisher) as well as the "Certificate of Occupancy" if required in that town. Not all towns require a C.O.
If the contract is making the buyer responsible for the C.O. it means that the buyer will have to arrange for the municipal inspections to occur and to make any repairs necessary to get the home to pass the inspections. This is unusual, but it is happening occasionally, particularly in short sales.
Make sure you have a good real estate attorney who knows how to protect you in the event serious/expensive repairs are required to obtain the C.O.