Our pet sitter charges £25 per night, but for that she stays at ours for the whole week/fortnight/long weekend/whatever. As Sheila points out, yes, you do have to provide your own food, litter etc, and whilst she's there it's our utilities that are used, but I think that's a small trade-off.
The charge is the same regardless of the number of pets she sits for, so when we had the dog and the cat, the fact Tess required walking and Paddy didn't, didn't affect the sum paid. She also feeds the birds for us and keeps the place ticking over nicely. We also get a little report of how everything's been.
I'm also fortunate because I dont pay the full £25.00 per night - we get mates rates as we've used her since her business started.
We love her, we do.
I agree - some pet sitters are hit and miss, and we interviewed a few who were quite unsuitable before finding ours, but we wouldnt swap her for the world. She came to see us a couple of times before we first engaged her services, so she could be a familiar face to the pets, and we knew from the way they behaved with her they liked her. It's been no difference since we lost Tess and Paddy and resumed with Mac, Ross and Tinky (although Tinky was a bit of a scaredy cat at first - he soon settled down with her though)