I love threads like this so much. It's one of the best things about this forum. Long may they continue.

Once I was about to bring my hoses into the house I was stopped by "I hope you're not going to bring those into my house!" as I was on the doorstep, overshoes on facing a pure white wool carpet in the hsl and with a dog running backwards and forwards along the hall (I was to do 2 bedrooms.).
(Incidentally I had estimated £65 on the phone and when I assessed the job it came in at £70, she kicked off big style. Oh, and it was a big 5 bed house and husband flew long haul 747s for a living. So the price was really academic.)
Anyway, despite feeling like replying "No,Madam, I'm going to lick your carpet clean!" I smiled sweetly and gave her the red-carpet treatment. Took the money and resolved never to go there again.
Why did I do it? There is a perverse pleasure sometimes in not letting the client see that they have annoyed you is one reason. Secondly this was quite a few years ago and I had nothing else on and it nicely filled up an hour or so. Finally it gave me yet another story which I might include in my memoirs when/if I get round to writing them.
Would I do it differently now? Almost certainly yes. Partly because of the knowledge and experience I have gained in the meantime and from forums like this. Secondly as I have got older I've found that it is easier to impose a natural air or authority in these circumstances which often avoids such issues occurring in the first place.
Having said all that I think Tihson is not far off the mark. If you can promote yourself as the solution to the problem (by being independent) rather than part of the problem, and in effect siding with the unhappy householder you can often generate loyal customers for life.
But as Joe said I think this was probably one customer who proves the rule that they shouldn't be touched with a barge pole.
Roger