I just partnered up with a general contractor who's going to come with me when view properties to give me an accurate estimate on repair costs.

In order to get an accurate ROI you should include these things.

The seller insists that a 2% of effective gross income allowance for maintenance and repair expenses is accurate because the building is "brand new".

It is almost impossible to model this accurately as this has never been done before.

How accurate would a projected number be--seems like the seller would want to make these projections as appealing as possible.

All the references to Chrestate aka Maysonet and the CEO are accurate; including being a minister.

The vacancy rates are also estimates, but I'm hoping a property management company can give me a more accurate estimate. 

Sellers can have too high an opinion of their property.If enough people keep making low ball offers the seller will slowly come to the conclusion that the buyers are more accurate on the real value of the property.  

@Konrad Lightner the absolute best way to know how accurate your lender's estimate for hazard insurance is would be to call a few insurance agents for quotes.

If those 100 data points cover 100 years, your model will be more accurate predicting the next single year than trying to predict the next 2-5 years.So I don't recommend trying to use an predictive model to try to forecast the next cycle (years), but I would rather use a predictive model to forecast the next short-term movement of the current cycle.