An important question here is, "how much like Tripadvisor?" If you're OK with a finicky low-end knockoff, you can probably get PHP programmers in the third world to do this for US$20,000. If you want something scalable, feature-full, and maintainable, with a good recommendation system, I would say US$200,000+, on the low end.
You'll need people, or an AI, to gather data for the site. I would recommend the former. Developing a good AI will cost a pretty penny, while data entry people are cheap, and once you get going you can crowdsource it.
Additionally, you'll need good negotiators to make any money with this. You can do it yourself if you're a people person, or outsource it to those who are. Again, the latter is going to set you back quite a bit.
If you're still interested, PM me.