The rate is debatable, but some sites such as Joystiq state that some "escorts" make as much as 10,000 lindens a week (which is about 20 USD? I am not sure about the current exchange rate, I don't play Second Life). My research has nothing to do with Second Life, but I thought sex on the virtual world might be something of interest to one of the other groups.
In this case, a young Italian woman (who is not a prostitute offline) decided to explore her strange curiosity on the internet and she made money. Though I found it interesting what she said toward the end of the article:
"In Second Life I look similar to the real me, even if I don't use the red hair extensions every day," Alderson says. "I try to minimize the differences between real life and Second Life -- my avatar looks like me because it's me that's doing these things, not a character or an actress."