A better idea would be to go to a local chain hardware store and see what windows they have in large stock. Those will be the least expensive windows you can get. You want the standard sizes that are mass produced for stores. Anything else is going to be more expensive per window.
Try watching some good old HGTV, they have great suggestions.
What you need is a contractor/installer that can get windows for you at a discounted/wholesale price from a local source. I have Polaris windows and love them:
They are available from here:
I would also suggest in stock at Lowes and Home Depot, about as cheap as you can get with a 10% off coupon.