I will use the bitcoin to buy some Etheruem and then buy into Slock DAO. After I have made some profits, I will give 10 bitcoin back.
I think if someone ask you that i give you 10 btc or something, so it doesn't mean that he will give you that amount, he is just telling you that he have some amount of bitcoins and ask you some advice what the best way where he invest it.
But I also do imagine, what I will be doing if I get 10 bitcoins for free.
Unlike he said I will not return back that bitcoins after gaining some profits unless he mentioned about anything of returning it.
As you stated OP must be getting idea of investments by saying about free 10 bitcoins.