I know that this service has profit as well but if some casinos will pay you for advertisement, I hope that it will still be genuine review that you're going to give them.
Good question, even with the best intentions at the start, what happens when an advertiser asks to tweak a review or move their casino up the list? Would be interesting to hear how you plan to handle that, for example by keeping ads and ratings completely separate.
There are handful review sites also in the forum from reputable people, and I think that they are handling it well when it's come to revenue.
But let's just hope that they won't be affected by the potential profit or advertisement they'll receive from those truly bad casinos and won't tweak the genuine review they'll give to them.
Because in the end, they can give some tips as there's always room for improvement.