[Highland Park] Rental Registration

I'm in the process of taking care of this rental registration for the city and I'm hoping that someone would be able to answer my questions before I trek downtown on Monday. I've only owned my house for three years. I currently live on the first floor and rent the second and third as full apartments. Also, on the second floor I rent a separate bedroom and basement bath (apart from the other apts). Does this count as a three or four unit dwelling? Next, the previous owner had a certificate of occupancy as a two-unit dwelling. Obviously, I'm going to have to get a new certificate of occupancy. Has anyone done this already and should I be worried about a hefty fine? Thanks in advance for any advice you can offer, Rachel