Thank you all for the responses and the fairly comprehensive list!

I would not say that you will ALWAYS get a value increase with the change.Second, the type of renovations you want will require you to pull an ALT-1 Permit: Permit's in NYCHowever, Jillian can confirm that.It is possible that a full tax re-assessment of your building will trigger paying higher taxes, which will blunt your calculated cash flow.If you were not changing the Certificate of Occupancy, I would not have mentioned a tax re-assessment.Those are a few things to think about and make sure you don't wind up spending a lot of money to make a change in the CofO only to wind up having the same Property Value AND having your potential income source blunted by increased property tax.

The new property tax for the property will be based off of the new purchase price and assessed value of the home.

@George Gammon, thanks for the comprehensive information provided.

For instance......checking proposed and special assessments in the area...a nearby pig farm etc. 

Even if they are expedition with the new home's structure including assessing building & zoning codes, 3 weeks doesn't account for the owner's coordination of design, layout, neighborhood research, etc.

If you don't want to get a Realtor involved to provide a professional comp, you can look at the other listings as well to assess yourself. 

Bluntly put - take a reading comprehension class for starters.

Tenant problems, repair problems, special assessments (with condos), etc. 

Wondering how much analysis and research is sufficient to make an offer and what details/assessments are better saved for the due diligence stage?