As you know, renovation/addition projects can vary greatly in price, depending on the scope and quality level of the construction. Rather than focusing on the price per square foot, I think it's more important
to make sure that the work you do and the money you spend are not out of line with the majority of homes on your block.. Whether you're planning to sell soon or in the distant future, you want to get a good return on your investment. Make a list of priorities for your project and then get several bids from contractors--their quotes will help you determine a reasonable price for the project.
I've lived through several renovation projects and I can tell you that as long as you're patient and keep a sense of humor, the end result will be well worth the time and money.
Really depends on the finishes and amenities you plan to add, i.e. plumbing, electrical , etc.
Call Leo Calderon 708-955-9229 with Caldero Construction or visit his website http://www.calderoconstruction.com.