A friend's father is rich. He wants my friend to save money, so last year February they made a deal: he'll double his savings by the end of this month (year after the deal). Now my friend is asking me for extra money so his father can double that as well, after which I get mine back of course. I have about 20k that I can 'borrow' him for a day.

I asked him: what's in it for me? He said: 2%.

He'll get 'free' money without doing a thing. If I don't 'help' him, he will not get the extra 20k.

2% on 20.000 = 400, which is nice to have. But he gets 19600 for doing nothing, while I'm the one with the risk. I feel like this is disrespectful from him towards me.

All thoughts about even getting my money back aside, how would you play this?