If your pricing is reasonable, i believe that the credit crunch could work to our advantage. One method i have used in the past is to knock up a self print leaflet listing the cost to hire a diy machine, the time involved in picking it up then returning it, the chemical cost on top, the fact that their day will involve emptying the small tank, lots of time. I then add on that all they have really saved is around £25 or so.
Then i add the punchline, is your time more valuable to you than saving £25
It makes them think, especially if you then state, make an appointment to hire the machine again real soon because your carpets will be dirty again real quickly.
False economy really.
Dave