In a typical 3/2 block house, there will be about 8-10 windows. If the windows are the older silver framed styles and/or they have window cranks, rehabbers will most likely replace them with the new energy efficient windows. These windows can run about $300/each so most rehabbers will budget about $3,000 to replace all of the windows in a 3/2 rehab.
Image source: http://www.awpwindows.com/energy-efficient-windows-houston.php (8/18/16)