1. Do It Yourself - You rent a small portable machine, use lukewarm tap water with 100 pounds per square inch (PSI) of pressure and a vacuum of 2hg. It may take you four to eight hours of hard work and your carpets will be wet for days. If you're lucky, you won't ruin the carpet. And, they will resoil quickly so you should clean them three or four times a year ($120).
2. Hired Portable Machines The major difference between this and "Do It Yourself" is someone else does the work, but they still use a portable machine. The result is the same-the cost is often double ($240).
3. Professional Truck-Mounted Hot Water "Steam" Extraction - The major difference is in the POWER.... The water is heated to 200o F, pressurized to 500 PSI and vacuumed up with a suction 10 times that of a portable machine, so carpets are normally dry in hours, not days. (This process does absolutely NO harm to your carpets if done correctly.)