This is a trap.

Especially if there is a man in the house.

$100 is a rent agreement. And, if you do not approach it like you are subletting, than you will end up in all kinds of litigation problems.
Basically, when you try to get rid of her, she just calls the authorities, and you are now having to go through litigation to get her out of the house.

Further, in most states, she just has to claim that she is being sexually molested/harassed, and the guy is removed from the premises, even if he is the owner.

It is a very bad deal. Especially if your state has renter protection laws.