Operating Expenses for a 30 unit multifamily

[Kam Su]

I am currently looking into a 30 unit multifamily complex for investment. This is a rundown complex which needs rehab. The target rental price is approximately $500 per month with electricity,water included. What is a good thumb rule for estimating operating expenses? This property will need a management company services to operate. Is 60% of gross rent a good estimate?

Here is a brief rundown on my estimates:
Cost to acquire/rehab : $600k
Rent estimates/yr @85% occupancy: $153k
Operating Expenses @60% of rent: $92k

Annual Cash Flow:$61k

Are these estimates realistic/conservative/over the board?

Thanks in advance for your help.