If they have money, though, I usually state my costs up front. Suddenly, they're not too keen on the idea, as they expected me to do it for free.
Can't count the times on mine/my family's and all our ancestors fingers, how many times people wanted me to move them for nothing after they'd asked what I did for a living (and befriended purely me on the basis of my being a removalist). Didn't matter how well off they were... in fact, the wealthiest were often the worst by far for wanting something for nothing/a free ride.
I didn't mind helping out those who were genuinely struggling, but it was real hard to swallow when rich people expected it. One bloke in particular, a rather wealthy banker type, even went to the extreme of having his wife cavort around in front of us in a scant/see thru negligee... in the hope we'd accept another kind of 'payment' for our services. When the job was (almost done) and money was supposed to be changing hands, I told him that, I had a family to feed and his fridge, freezer, washing machine and dishwasher would be staying on the truck until he paid us the cash owing in full.
His threat of calling the cops, was met with being told: "Sir, I used to be with the QLD Police, and there are serious consequences for offering to pay for professional services via prostitution.", so without further ado he coughed up our fee plus an extra $100 from the fattest wallet I had ever seen.
So, it doesn't matter what profession you're in, there'll always be somebody wanting a free or cheap ride. As for the disrespect, well human nature dictates that occasionally we're gonna cop abuse and little or no thanks from some quarters, no matter how well we do our jobs.
Oh, and the rich banker swine got what was coming to him... about a month later I was moving his wife, who's obviously had enough and was leaving him.