Doing something that seems charitable or altruistic, but is in fact done with the hope it will increase your chances of getting laid.

1. Blue Monday is the most depressing day of the year, calculated by Dr. Cliff Arnall, a researcher at the University of Cardiff's Center for Lifelong Learning.
Factors used to calculate the date included weather conditions, debt level, time since Christmas, time since failing our New Year's resolutions, low motivation and feeling the need to take action.

In 2005 the date was calculated as January 24th, in 2006 it was January 23rd, and in 2007 it was January 22nd.

2. A song by the hard rock band Orgy from their album Candy Ass.

Evading legal repercussion by showing up with a camera to fuck a hooker. You pay the camera man/producer the agreed upon amount and he pays the hooker. Then you work for free or "Pro Boner" to make the adult film.

work completed with sexual favors given in recompense

For the good of the penis

When you do a task, or job for free but instead want that person to love and have sex with you

When a prostitute gives their service for free.