There are a lot of novice carpet cleaners out there giving advice. Larry Cobb is a Chemist that has grown up in the carpet cleaning business. He owns Cobb Supply. I would take his advice without question. Here is a pretty good thread in this forum you might want to read.
As I stated in this thread--agitation 175 rpm buffer (available on craigslist for $100-300), good chems, basic dual two stage Mytee Breeze that you can easily upgrage to dual 3 stage later for $250. Upholstrey tool, stair tool and a Vac. You will be able to clean anything.