Yes my brother. There's nothing wrong with that. As long as you two are not related by blood. What's more important is; do you two love and like each other?
Love and like are two things that go together which is also needed in any relationship. Love brings people together and 'like' is what sustains the relationship.
So yeah, if both of you are confident about each other, then it pleases me to let you know that you can go ahead and propose to YOUR LANDLORD'S DAUGHTER. Have no fears my brother.
All the best,