I always hear this form of the request with a bit of bemusement. The simplest way to add $100K to your income is to rob a bank. You didn't constrain the problem to "legally" :-)

But setting that aside for a moment, why $100K? What does $100K get you? And why is money your goal? Do the thought experiment where "Poof!" the magic genie drops $100K on your bed. Sit there and look at it, now what?

You need money to pay the bills and survive, okay. But having it is rather fleeting, and when you die you cannot take it with you. Get past "money" and into "accomplishing something." When you have something you want to accomplish come back and we can opine on that :-)