Average cost to build a house

[Joe Kalis]

I was Riding my bike today and noticed a bunch of plots of land for sale. Some we're big enough for 2-3 houses, and it just made me curious what the average cost per square foot is to build a house from ground up. Obviously it's going to vary by market and perhaps even by what type of market or swing in our economy, but I'm in the NW suburbs of Chicago (Wheeling) and just curious if there's a general rule of thumb to estimate how much it would cost to build a new house. Let me know!