From the link provided by Tail wheel
There is another wannabe commercial pilot posting here curently about the same thing.
See: Legal implications should an accident happen
All I say if a member of the public pays anything for a flight with a stranger be it a donation or whatever then the least they deserve is a commercial pilot operating under an air operators certificate.
Bob, just because I ask a question, how does that make me a 'wannabe commercial pilot'? An apology would be graciously accepted