A question like this has a sense that the person won't mind. So, oddly, either "yes" or "no" can mean "yes."
You can say "No, I don't mind," or you can say "Sure." They both mean you can have the money.
If you want to deny the request, you have to say something like, "No, I'm sorry, I don't have it to lend right now," or something like that to make it clear the answer is "no."