How can I calculate the cost of building a 4 unit apartment building

[Chris O'brien]

I live in a small town with very few apartment buildings. Apartments are hard to find because there are so few of them around here. Apartment buildings never go for sale because they are cash cows. I want to build a 4 unit apartment building. I have construction experience but no experience running the show. I am going to do this using cash. Building costs are relatively cheap here, it is a pretty rural area. How do I go about calculating building costs?