@Mike Terry sounds like a pretty good argument to go after the property, I think your question is more along how to value it, and account for the deferred maintenance. Sounds Like you have the operational experience to turn the place around and make it a winner. as far as figuring a proforma here's my logic. Not sure if its "too basic" but its where my mind goes.
- I'd start with the end. What do you think market rents are for a turned unit, or fully improved property? Then figure aprox what your refi numbers/value would be given those rents/expenses at a stabilized point, and that to me is your "all in"
- From there it becomes an exercise of what it will take to get to that point or property condition? and subtracting that from your end value + whatever equity buffer you want to account for.
- If you're going after a seller finance deal I think once you understand what it will take to get to a finished state its simply a matter of aligning your needs as far as short term cashflow with the current rents/situation, with the net number the seller needs after the refinance.
again that's just how I think about it, maybe its over simplified, but that's where my logic goes.