I occasionally will work with people for a variety of reasons without pay, mostly for honing and developing my skills. The reason for this, is because I do not believe in "learning" off of my paying clients.
The only way I will take a commissioned job is if I know without fail that I can produce the end product. I get a lot of requests for unique composite work. So I have to really practise this style under many different types of lighting conditions and blending with back plates.
Here is a couple of art pieces I recently worked on.