Find free carpets by checking ads in classifieds, such as Craigslist, for people who are giving away carpet they no longer need. Large buildings, such as apartment buildings, may also be a source of free carpet, as they often have leftovers after doing renovations.
Many carpenters finish jobs with a considerable amount of leftover carpet. They are often willing to give the carpet away for free to people who are willing to pick it up, as they have no need for it. Large home renovation stores are another possible source for free carpet, as they get rid of old rolls as new shipments of more recent product lines arrive.