Why do we not hire our military out to other countries?

The debate in Washington never seems to involve reducing the military. Even discussions about reducing the military budget do not actually talk about cutting it, only reducing the size of the increase.
So, if we do not seem to think we can reduce the size of our armed forces why not rent them out?
Why be the worlds policeman for free?
Pay us to pull your ass out of the fire or burn in hell, your choice.

We can continue to support them until they get on their feet and as they bring in more money, we can reduce the amount that we invest in them until we reach a point where they are self-sustaining! And, if we can reach that point, then maybe they can actually produce a surplus and help support the society that supported them.