The simple way out of that conundrum is to make it free to list (perhaps with an option to upgrade to a "premium" listing for a recurring fee), and charge for t

The simple way out of that conundrum is to make it free to list (perhaps with an option to upgrade to a "premium" listing for a recurring fee), and charge for the actual bookings made through your site (you'd need to experiment to figure out whether flat fees or a percentage worked better for you).