I did warranty work for Cal Spa, Coleman, Jacuzzi, HotSpring and Sundance when I first started my business. I needed work, and even though I made less per call, it was a nice flow of cash. I frequently had to go back to the stores 2 or 3 times to get paid, and it was often in cash....
Now, I stick to warranty work mostly. I have some outside guys who do any non-warranty stuff that comes in. But they will do warranty for me in a pich - as a 'thank-you' for the other work I send their way.