I am exploring the idea of adding square footage to my downtown duplex (above the crosstown in the West Side neighborhood). 

However, the residential part must have greater footage than the store--check with your mortgage broker.

$7500 for what appears to be ~0.5 acre fenced lot, two homes, one listed as rent-ready and one needing some obvious work just from looking at the outside during a walk-by today.Just based on perceived square footage of the smaller "rent ready" unit, I estimate that I could get it rented fairly quickly for anywhere from 600-750 per month, depending on the interior and based on what I've gotten for other units in the area.

You can get a good idea of the cost per sq. ft. and multiply that average number to the square footage of the property you're interested in.For example, if the triplex is 3500 sq. ft. and the average sq.ft. number for similar properties you've come up with is $100: 3500 X $100=$350,000.Of course, there are other factors such as lot size, year of build, etc.

We added square footage to the home by popping the top and adding a second floor.

J Rod,I don't know the total square footage.

Families that want the square footage and less-urban school districts locate further from downtown.

Im would like to know some ways to accurately analyze a property in a timely manner given say 1-2 comps sold within 1 year in a half mile radius and widely spread square footages.

I keep track of who pays utilities, square footage, etc as well.

An appraiser my not include the square footage of the addition in the assessment of value.