I trade slip for use of the vessel. It has worked well for me.
Be a little careful in your choice of consorts for your favorite girl. No worse than vetting boyfriends for your daughter!
Marina fees will eat up your boat in a few years anyways. When I advertised for a partner I got over 15 replies. I keep my boat with a property owner on a canal in SW FL. He uses her when I can't. Maybe I am just lucky but I am pretty happy with the arrangement.