apartment investing

[Daniel Etheridge]

There is a property I was looking at priced at $875,000. It was appraised at $1,200,000 and that was with a 25% occupancy. The building was previously used for several businesse offices. The zoing was changed to residential (multi family). The building was originally built as an apartent complex.
32 of the units currently need rehab. Which the estimated cost totaling $166,000. The average rent is $600 dollars. It is a 54 unit complex. Here is my question. What questions should I be asking the owner and how do I figure what this building can possibly cashflow a month.
I have plenty of experience in residental but not multifamily. How do I determine what would be a good investment and cover my debts and still allow me to cash flow. I have a basic knowledge and understanding of multifamily but I want to know more!