to add a bit of a freelancing spin to it - theoretically you could charge him to use the camera. If he were to need a special camera for a shoot, he would need to rent it and pass that cost on to the client. Your situation is not much different. Under these circumstances you would be best served by having a written agreement to cover the hire + what happens if the camera breaks. You would also need to declare the extra income.
Moving to a philosophical angle:
Of course, he's your friend, so you'd like to help...
Or would you? You say "On the other hand he is asking me for help frequently", so perhaps you would prefer to say 'no' but feel guilty about it?
My grandmother had also had a saying: "You teach people how to treat you". If you're feeling taken advantage of in this friendship, perhaps it's time to set some clearer boundaries.
Combining the two, perhaps you could ask for a non-financial return, say get him to buy you a few drinks / lunch / take photos for your personal use in return. That way your help is being acknowledged and valued and you avoid the complications of a financial transaction.