Ian
With respect because I know you have a carpet cleaning business - if I asked those questions relating to carpet cleaning I would possibly be laughed off the forum.
If I employed a pressure washer (I wouldn't because I am one) and they turned up and said where's the plug socket I would tell them to p*ss off - that is the equivalent of a Rug Doctor!
There is no training for pressure washing - if you want it get a CSCS card (about forty quid) and I will give you free days on my works
The market is as diverse as carpet cleaning and the pricing structures reflect that - I would put it on a par with carpet cleaning, with a lot more mess.
I can use up to 10 000 litres per day, on my own so it is impractical to take your own water, some working local may take their first tank and then use the clients water supply.
Is there a downturn in carpet cleaning as the CC's stampede down here for all of the tricks and is pressure washing seen as an easy clip on, to assist struggling businesses because as you say 'everyone seems to have it on their vans these days'.
You need to give a little more than your post to be taken seriously, in exactly the same way that I have seen on the carpet cleaning section - that is why you have had roley eyes and smiles.
I am glad I am not in domestic pressure washing!!
Rob