There is no such rule to separate self unit from rental unit

As long as you use the concept of leveraging, there is no such rule to separate self-living unit from rental unit. It's common practice for people in inner city cores to combine self-living and rental unit. In European cities, many people bought row houses on busy street, owner live on the second floor, the 1st floor is rented out to businesses. No matter how you manage it, as long as you can leverage rental income to pay for mortgage payment, you are in a business to get yourself rich, it's that simple.