It sounds like you already own a two family and simply want to do a condo conversion.
1. Call Max Schechner - 781-935-1818. He is a real estate attorney who specializes in conversions.
2. He will recommend an architect who has to draw simple plans.
3. You will need to make sure you have utilities properly separated.
4. Assuming you are doing this to sell one or both, call me for values!