Slayers serve under the counsel and not even of their own free will as Faith was for the Mayor. So they're doing someone else's work as well.
Yeah, but that's hardly the same thing, is it?
Faith CHOSE to work for the Mayor, she didn't have to do it and as she was, she might have felt like it was an actual job, whereas her work for the Council wasn't really work at all. She was there tool, sent to where they wanted her and her life wasn't her own. That's why I think it's different when she accepted things from the Mayor, because she thought it was an actual job where she deserved to get paid, so much different to her Calling, where she was literally picked off the street.
@ILLYRIAN said: Yes, but she would have been working for The Watchers Council as a slayer.
Her 'job' for the Council wasn't even remotely similar to what she had with the Mayor. The Slayers don't 'work' for the Council, they are tools and weapons that they use how they see fit. It's one of the main reasons I think that Faith rebelled so hard in the first place.
And, again, as [MENTION=12171]Ethan Reigns[/MENTION] pointed out, Giles never, ever gave Buffy cash - not until S6 when he felt she needed it. He was just lucky that Buffy had the life she did when he was assigned to her. And that might have contributed to his feelings towards Faith. Buffy didn't need him, because she had her own life, so maybe he just assumed that Faith would be the same. After all, he had no experience with Slayers other than Buffy. Even Kendra wasn't an open book with him, we have no idea where she lived. Her Watcher might have kicked her out the second she was Called or turned 16, whichever came first. We just don't know.