I was planning on making a $100 bill cake, but does anyone know if sams club would do one for me & sell it? Someone said walmart does and I checked walmart but they said that they wouldn't

Have you tried asking them?

Well I just thought of it last night so i couldn't call them cuz they were closed BUT I did call them this morning and they don't

Do you just need an edible image? Back in MI, the cake supply store I went to would let you buy images from them.

...or are we talking about something different altogether?

Perhaps they are concerned that it illegal to copy the bill.
http://www.bep.treas.gov/historicallegislation.html (scroll to the bottom of that page)

It is legal as long as the image of the bill is less than 75% or more than 150%, and one sided. You could print out a copy of the regs when you go to get an edible image to help assure them it is legal.

It might be a company policy not to make them.

Nope, Sam's Club will only make cakes as they are pictured in their book. However, ask if they still have the dollar bill edible image. I remember we had an edible image of a dollar bill that was actually a frame so you could put someone's picture on it. Obviously it wasn't an exact copy of a dollar bill, but the same idea. I can't remember if we still have it as I haven't made one lately.