ok so my response could be seen as taking the p, but no more than what you are doing to your customers when offering a professional service and using a vax.
Our cleaning company also offer a wide spectrum of services, carpet cleaning being one of them. When I decided that I was going to offer this service, I studied what was needed, training, cleaning methods, machinary, chemicals, ppe et al and then used forums like this one for guidance. Only then did I start to clean carpets.
I soon realised that the henry george, vax, rug doctor type machines are not good enough for the job that we deliver, and are basic domestic machines. Perfect if you want to just want to freshen a small area in your home after an accidents but thats it. Im not suggesting that you go and spend thousands on a machine that might only come out once a week, but something like the machines being advertised at the top of this thread are the ideal entry level.
Hope this is more helpfull