Interesting question. From what you are saying, it makes me wonder what your reason would be for wanting to have your content indexed?

If you do decide to do it, you are definitely putting both sites at risk IMO. Even if you take all of the precautions to tag your content as the original source, you will likely be damaging the money site as they would risk losing visibility for the content you are providing.

I would want to know a little more about the motives and objectives of each business, but my initial recommendation would be not to do it based on what I see here. It has the potential to damage your business relationship.

If you are trying to take the business away for yourself, the answer might be a little different and would need to be very carefully thought out.