Wow there is a lot going on there! First I would ask if people are on term leases or month to month. Sometimes older owners don't even have leases, they just collect rent and hope for the best, so that would be my first question. Make sure you are running your numbers on what they ARE collecting and not what they SHOULD be collecting, that will be a huge difference. If he is shoving a proforma down your throat you can tell him to pound salt, you will have months of evictions, renovations and attorney fees to deal with before you ever get to a proforma number. Find out local tenant laws and know how long the process is going to take to do the evictions. Make sure you inspect all units to get a true idea of condition before pulling the trigger on anything. The one decent unit they show you should not represent the other 7. An agent told me this and then I found a 400lb pig living in one of the other units. Never trust a sellers agent, never.
You have a lot of work ahead of you but this could be a fun and profitable project if you get it for the right price, and have a good attorney on call.....