It depends on the extent of the damage. Carpet cleaning can be surprisingly effective if you employ a professional to do it. When I moved into a new home, the carpets were also in bad condition. However, I didn't have the budget to buy new ones, so I consulted a company that offered carpet cleaning in Chippenham, Wiltshire. After looking at the carpets, they said that they could improve them significantly, and they did.
They managed to remove the bad smells and stains. The carpet also changed colors by about four shades after the cleaning, because it had been so dirty, to begin with. I still intend to replace the carpet at some point, but they're perfectly functional and clean for now. So if you're on a budget, cleaning is definitely something to consider as it will probably be able to turn your dirty floors into something livable for the time being.
