Do you have a detailed current rent roll? I'd try to get this information so you could not only accurately determine the income per unit, but also find out the vacancy rate. The more historical data you can get, the better you can estimate vacancy. I agree, seems like a low OER (operating expense ratio) for the property type. Is the property self managed since no management fee or on-site management salary is being reported on the expense side? I'd try to tie down the rent rolls, occupancy and above the line expenses. Vacancy and collection loss are very important in either a direct cap or DCF analyses.
What kind of lending terms are you being quoted? I only ask because you could use the mortgage-equity band of investment and debt coverage ratio to develop a cap rate based on "you" and compare to any market caps in your area. You can also use the lending terms to include a loan in your DCF to calculate your leveraged cash-on-cash returns.