A lot of it depends on who the person is and how much advanced notice they have.. I use to babysit a lot before DD1 was born and right after she was. If I had some notice it was usually either dinner (if Im babysitting for a close friend) or 7-8 an hour. Usually it was a military family (I was a Marine at the time) and I knew how hard it was to make ends met so I didn't charge them much.
Ive never paid for a babysitter for DD. Shes stayed at one six times, twice for date dates and 4 full days when DD2 was in the NICU and I was at the hospital with her. All 6 times I exchanged favors with the people watching her or they did it for free. I always offered to pay but they never accepted.
~Heather~ Mama to Miss E (1/07), Miss A (11/08), Mr.T (2/11) and Miss A (10/12) Expecting our newest blessing sometime late Sept/early Oct.. Wife to my Marine since 11/2005