Get yourself a picture frame.
Step 1: Picture Frame
Get a picture frame. Put a picture in it and another on top of the picture.
Step 2: Arduino
Tape a arduino board on top the paper and tape the paper and picture together as well.
Step 3: Money
Put some money under the paper.
Step 4: LED
Put a LED in the 12 and 13 spots of the arduino board, so when you lift the paper, the light will come on.
Step 5: Final Product
Lift up the paper and your hidden money will be their.