I have a Mytee HP60 Spyder for several years. It has an internal water heater, big 3+ gallon water and recovery tanks, on wheels, great pressure and water lift.
I never ceases to amaze me how much deep embedded dirt it can remove from carpeting and cloth seats.. My water recovery tank always drains out dark brown to black water which is all the dirt that was in the carpets or cloth seats..
I also use it to rinse again and extract all the dirt out of Convertible Tops.. It really does a great job there too, and helps them dry faster before I apply the Conditioner..
This particular machine is big enough to come inside and do some carpet cleaning. It will never be able to do as good and certainly as fast as the guys with the big van with big machines, but it can do fine if you are willing to take the time to do it inside..
It is easy to open up the top half to expose all the motors that it uses for maintenance. I have never had to do anything to mine except rinse it out really good including the vacuum hose, and occasionally run some distilled white vinegar through through it to keep it clean and remove whatever may build up in the pressure hoses and pump..
Good luck with your research !
Dan F