Well its your prerogative to help him or not. I think you can help him with your extra funds or profits if thats fine with you but also you can tell him that you dont have money for the help or aid his asking its quite simple. A friend will understand the need of one, it depends on how your friendship matters actually.
Thanks for this suggestions, may be next time I will just outrightly state to him or any other person that comes with such requests that I have no available funds to help them with, because this days alot of those who can't manage themselves in terms of financial dealings are now bordering the decipline forks with they financial crises, I remember many times I advice this my colleague to invest his money on assets, but rather he prefers to buy things that have not long term values.
But at the moment I have loaned him the money but with high interest rate, this way he will be put under pressure to pay back on time.
That would be more better reason for them to stop asking further question why you can't grant their request since for sure they understand your situation if said reason is you had no funds available left in your wallet. I use that reasons if I know the person who tries to lend some amount on me is not a good payer. Although I'm not the type of person giving advice about investment since I don't want my statement will be bad for them especially if they don't understand my point but its good that you open up this topic to them and maybe they consider to look at it.
Hopefully your friend will think about paying you since sometimes there are people that only good when borrowing but didn't bother to pay when stated pr negotiated deadline came.