I don't do carpet cleaning but I do know 2 excellent guys that do this, both make a reasonable living but both said it took a couple of years to get established and bring in good regular income.
I pressure wash and this brings in good money, again if your starting from scratch then it may take time to build up, I had a window cleaning customer base of 1000 to help jump start the pressure washing side.
Either way don't underestimate how much time and effort and money advertising it's going to take before you start getting a steady return, also buy the best you can afford, cheap equipment will not do a job to the required standard or last, but by the same token don't go throwing money at stuff you just "want" only buy what's needed
Darran