i agree with Goron,
most customers are not remotely interested in the machine you have, just whether you do a good job at a decent price and are a nice person, and thats within any ones grasp!
You seriously dont need a t/m to run a good carpet cleaning business unless you do alot of commercial work, a porty will do the job, unless you are a perfectionist who wants to get every tiny grain of dirt out :

We ran our business for 12 years using porties and kept our customers happy over that time, those same customers either get the t/m or a porty depending on the workload, and i've never had anyone notice the difference.
If you want to do the job in half the time however then thats where the value is ,but if you haven't got the workload to go along with that then whats the point?
If your prices are right then you are prob only doing 2 to 3 jobs a day, easily possible with a porty,
We run two t/m's now but really only because we do work for the local council, that needs doing in a short space of time and covering a huge area !
Would i give up my t/m now, not likely, but its a luxury you get used to

steve