Would you rather take help from someone who's doing it for free or someone who's charging you for it? Is it a common (and proved?) notion that free has no quality?
So let's say me being an android developer want to help someone in my spare time but don't want to go through the pain of freelance websites and registrations. Would you believe such a person and ask help or just think that he/she must not be good enough.
There's risk of lawsuits if you accept help like that. Best thing in your case may be to contribute to free (as in speech) software Android apps (perhaps Firefox needs more hands?).