Good question, I think there are quite a few different revenue methods which can be done without much disruption to the user. For example companies paying to get more control over their page and profiles.

One of the nice things is that advertising can be in-app rather than external, for example ads for a restaurant/hotel will direct to the product in the app rather than an external link.

Only after getting a solid userbase will I start to actually implement any monetization.

Also planning to put some measures in (if the app gets big) to make it so that fake-looking users or users with just a couple of ratings don't have their ratings count towards averages and predictions.