Looking for Calculator for New Build - 12 Unit Multifamily

[Kim H.]

I am looking for a good calculator/spreadsheet template for estimating costs for a 12 unit multi-family (everything from preparing the land, up). 

I have a 9 unit multi-family and there is space on the same property to add 12 new units. I am just trying to look at costs to see if it makes sense but I want to make sure I don't miss any pieces of the puzzle. 

These would be a 2 story building with stairs (6 units upstairs and 6 studios downstairs that could be converted to office/retail down the road, if it makes sense). Around 880 sq feet each. My property is on the main street of an old town area that is being revitalized. 

Just trying to wrap my head around around the potential costs before I make a decision.