I don't have much of an answer but I'll put my 2 cents in anyway.
I've thought about a cleaning service...I also read "Nickel & Dimed". If I were to pay for help with cleaning, I'd try to find a person not a company. Preferably a friend of a friend, at least a word of mouth recommendation. Second, I'd be clear about what I want and don't want. I don't want "spotless". I want "good enough".

As part of that we'd discuss payment, and that's what I'd pay, tipping wouldn't be necessary.

That's my little fantasy world anyway. Maybe it doesn't work like that in real life!