Hi Unique
I could say buy my machine buy my machine, but the guys are absolutely right, you should find out precisely what system is going to be more appropriate for yours and most importantly your clients requirements.
What market are you headed for,domestic or commercial? Who are your operatives, women or men? If commercial are drying times more of an issue. Is quietness of operation an important factor? Extraction has the versitility to deal with Upholstery, curtains, as well as carpet, but the downside is in general it takes longer to dry.
Hot water extraction whilst being a great and versatile system is only one process of many available out there.
All systems have negative and positive attributes, and none is best in every scenario. Often it is a case of horses for courses, and eventually you may build up sufficient kit to be selective in the most appropriate process in any given situation.
Hope that gives you something to think about.
Regards
Robert