I think we're talking about different things. Did you do freelancing on Elance/Odesk/etc?
I agree that doing a useful real world project for learning is great. If you get paid for it, it's even better. But cheapass clients on those websites are usually a different kind. People want to have a {popular thing} clone or {popular thing} meets {another popular thing} and don't really understand neither what they want from the freelancer nor what they want as the final delivery. Of course, there're good but cheap projects on those marketplaces as well. But as a beginner, it's way too use to stumble upon let's say... not very pleasant clients. Thus if money is not the issue, I'd recommend going the non-profit way instead. They at least know what they want and usually appreciate your work.
I agree that doing a useful real world project for learning is great. If you get paid for it, it's even better. But cheapass clients on those websites are usually a different kind. People want to have a {popular thing} clone or {popular thing} meets {another popular thing} and don't really understand neither what they want from the freelancer nor what they want as the final delivery. Of course, there're good but cheap projects on those marketplaces as well. But as a beginner, it's way too use to stumble upon let's say... not very pleasant clients. Thus if money is not the issue, I'd recommend going the non-profit way instead. They at least know what they want and usually appreciate your work.