A Certificate Of Occupancy or better know as a C of O, represents that a municipality is aware that a home is legally occupied and conforms to zoning and minimum repair and maintenance standards as of the date the C of O was issued. Below are five things that it ensures
1) Plans have been properly filed with the building dept before any construction took place, or if construction was undertaken, that the building dept is satisfied that the homeowner performed the work within compliance of the law.
2) Architectural drawings have been filed and the building dept has determined that they are in compliance with the setback requirements. These requirements are unique to every municipality you'll have to look into them.
3) If there have been any additional bedrooms added to a property with a septic system rather then a municipal waste system, Health Dept approvals were obtained for the expansion of the premises and the spetic system is adequate to serve the expanded needs of the property.
4) The plumbing and electrical inspectors have examined the property to determine that all improvements meets the Bulding Code regulations at the time of the inspection.
5) The Building Dept certifies that the addition has been completed in accordance with all codes, rules, and regulations and have been properly inspected.