The requirement "the property was not used as a residence for an part of the year" is a little ambiguous. The rental units were not used as a residence, and I allocate only the expenses from those units and allocate per square footage for any building expenses (like roof patching.) Why would this be any different than someone owning a couple condos (which would clearly not have been used as a residence.)
Thank you in advance.
Yes, the Safe Harbor elections are available for a multi-unit property, even if the owner lives in one of the units. There is no provision regarding the property being used as a residence for any part of the year.
Although you live in a unit that is connected to the rentals, that provision is referring to a "Mixed use" property, where something is rental one day, but personal use another.
Since you keep your unit and the expenses for your unit separate from your rentals, never sharing a rental with personal usage, you could use the Safe Harbor rules if you meet the other requirements.