I am paying "Occupancy Fees" charges and have rented the unit. Question - is occupancy fees that I am paying to the builder tax deductible expense despite getting rent.

Yes occupancy fees are tax deductible for a property you are using to generate rental income.

Ok. Thank you. What happens when the property is not rented.  Can occupancy fees be claimed as an expense? 

No, not if you are not using the property to earn income.