Before I sold my house I had home depot recarpet it. LR, hall, 3 bedrooms, 4 flights of stairs. $1200.

You can save some money by taking out the old carpet and pad and disposing of it yourself. But I didn't do it that time.

Make sure that you choose an FHA approved carpet, or none of the effort will be worth it. Some of the less than FHA carpet might as well be used as sheers on windows!

The big box stores have in-stock carpet for ~$1/sf. Pad and installation are on top of that, but you could have it installed within a week.