You shouldn't charge your friends for using your bed.
Matt's friend is in town and looking for a place to stay and Matt has a spare bed in his house.
Matt wants to tell his friend about the bed in his house.
Matt tells his friend he can stay in his bed for free.
Matt tells his friend he can use the bed if they pay a fee.
Matt's friend will think Matt is generous.
Matt's friend will think Matt is greedy.