What's the possibility of cheating a betting site or casino.
But to be sincere, I can't give an accurate respond to whether I'll cheat or not until I am caught up in the situation, what you term cheating may not be so to me.

Once a casino was having a down time, the where to pay me 72$ but mistakenly paid 20$ over, I know so many person's would say their luck had shone on them but I made a report and I was awarded 2.5% of the 20$ that is 5$, it may not be much but at least I got my dignity and self respect, imagine if I didn't make an attempt to return the money and the eventually get to find out (I doubt they'd have found out though)