You should never print an ad like that, if for no other reason than someone will vandalize your property. That exemption, from what I have heard, is to make it so small property owners do not have to conform to every single code and rule that big properties have to. Like handicap access and things like that which would require a lot of money to update to code.
If you don't want to rent to families, then 1 br apts are the way to go. 3 br units tend to attract people with kids or roommate situations.