I would be concerned about that. If you are renting it out, and there is an accident or a fire, it seems to me that you are pretty vulnerable to a lawsuit if the unit you own is not "legal". I own five rentals and try to make sure that everything is safe and pretty close to code -- steps, handrails, smoke detectors. My experience is that the municipal inspectors can get pretty nasty when they find an illegal unit on premises. They probably would not make someone tear it down, but I have seen places locally where a builder tried to sneak one over on the building department -- state duplex really a four-plex and the city shut it down bigtime. The builder went broke. And those people who bought it, to finish it, had to really jump through hoops to meet the demands of the city inspectors who were mighty angry. I always think it is best if the person who fooled the municipal inspectors is the one who has to deal with them down the road, such as at the time of a remodel, versus some poor person who bought an illegal unit. Just my take on this!