What does the term 'vacancy/credit loss' refer to in net operating income?

The term 'vacancy/credit loss' specifically refers to the income reduction that occurs when there are unoccupied units in a property. When units are vacant, they do not generate rental income, which directly impacts the net operating income (NOI) of the property. This concept is crucial in property management and real estate investment, as understanding vacancy rates and the potential for lost income helps in budgeting and forecasting financial performance.

In the context of the other options, total income from all rented properties reflects gross income rather than the losses associated with vacancies. Costs related to property maintenance pertain to the expenses required to keep the property in good condition but do not account for lost income due to vacancy. Expenses incurred from tenant defaults relate to losses from tenants who fail to pay rent, which is a different aspect of property income management. Thus, 'vacancy/credit loss' specifically highlights the income impact due to unoccupied spaces, making it the most accurate choice.