With vacation rentals, you have to have people who actually rent stuff and that's the part of the chicken/egg problem I haven't solved yet. While I was able to bootstrap the site, the traffic to it was non-existent thus I felt guilty if I charged people to list. The premise was that they would list for free first, their listings would attract traffic, then I would charge people to list. Meanwhile people are booking and more are listing - that was the idea.