I'm looking to get back into carpet cleaning after a few years away from it. The last time i used a hwe portable. But on big jobs, i seemed to spend all my time either filling or emptying it, as you can go through a lot of water on hotel, large office jobs etc. I see the attraction of the truck mount as you just pull the hose and in you go. No unloading the machine, filling up with hot water (if any hot water at all some times),
Truck mounts are pretty expensive but there must be some pretty decent second hand ones around, just to start off.
I remember when i started in 1998 ish, a company had a mercedes van with a truck mount that you could borrow for a week as a demo. I have looked but no one seems to do that anymore. try before you buy !