It is depends on many things like what is the wall finish inside (sheetrock, plaster, tiles...) and outside (wood siding, vinyl siding, stucco...), also price of the widows can very. For basic standard you need to calculate min. $300 (window and labor) for retrofit (fits into old opening) and min. $600 (labor and materials) for installing a bigger window. Installing a smaller one could be more expensive. If you need free estimate please let me know. I can send one of the contractors I work with. Low price and good job guaranteed. And of course if you or anybody you know needs real estate service I be glad to do business with you. All referrals are greatly appreciated. Should you have more questions you can shoot me an email.