If he does pay in cash, make sure to verify every bill. Feel the collars of the shirts of the picture (there is a definite texture there), observe the color shifting ink that notes the denomination, look for random red and blue fibers, of course, the water mark, and if you have a black light, anything from a 5 to a 50 has a special stripe inside the bill that shows up under black light and also has the denomination written inside of that stripe (20's are green, and 50's are blue/purple I believe). I am not 100% sure the 100's have a stripe like the other bills that shows up under black light, but I think they do have the same stripe noting the denomination.
