What is the correct way run numbers on multi family apartments?

[Chase Keller]

Looking to syndicate a deal on a 35 unit building.  How do you accurately calculate the numbers so you know what number makes sense to purchase?  Is there a clear formula to use?  

Basically we have the occupancy rate (which is terrible) at 60%, 35 units.  Asking price is 475,000 and we believe the existing mortgage to be just shy of that.  The taxes are 21500.  For cap Ex, management, and vacancy is it safe to use 30% for them all?  Has anybody found an easy way to do rough numbers on insurance per unit?  Utilities are paid by tenants (gas & electric)  This building is in a C/D neighborhood.  Property has been for sale for almost 7 years.

Any constructive feedback is much appreciated so we can learn how to do this the right way from jump street.   

Thanks!