It depends on the vehicle, but the general fee is 10% on rewards. Only rewards are tagged with fee. So no earning then no fees.
How do I sell my share(s)?
That is currently not supported. It's bit more complicated to do since some investment vehicles like strongblock does not allow for withdrawal of initial investment. However, we are working on a way to make that possible but it needs to be fair to everyone so will take some extra thought.
When do we get paid our rewards?
One time per week. That way we can save on gas and swap fees. However, that could change if the DAO votes for that to change.