Evidence disposal is the type of business that can get you a lot of money really fast, but is unlikely to be very steady unless you know the right people.
Fortunately for you, Howtomakeadollar does know such people.
1. Go to a big city
2. Go to a subway station in a bad part of town*
3. Wait around until well after midnight
4. Soon you will see some thugs fleeing the scene of a crime.
5. Approach them
6. Offer to get rid of the evidence for a dollar
7. Make sure they do not shoot you
8. Take the evidence and throw it in a lake. If the evidence can swim, you may have a difficult time, but you should be able to manage.
9. If the evidence looks like something that someone might want, you can feel free to try to sell it somewhere.
*Pretty much all subway stations are located in bad parts of town