Richard,
If money is tight as you say then a drier is neither essential nor even necessary. I have a couple of driers but I don't use them (I use a low moisture method of cleaning carpets) on upholstery. They are very noisy, take up a fair amount of space in a room (and van) where you have already put a fair amount of equipment anyway and they blow ornaments, pictures and dust around.
In short, if you're just starting out on a limited budget spend what funds you have on the best machine you possibly can and towel the suite down after cleaning. It would, in my opinion, be better to upgrade your cleaning machine with better vacuums etc, you'll get a better result and longer drying times which is better than a poorer cleaning result with fast drying times.
Nobby