Need a funny/clever analogy for "red light district" activities

[HighStakesPro]

For a class assignment, I need a clever analogy for something like prostitution, gambling, drugs, or anything else in a red light district.

Example:
Prositution is like peanut butter; they both spread for bread.
Prostitution is like fishing: you never know what you're going to catch.

What are some good analogies for such activities? Give me your best (and worst).