AI fee for timeshare rental?

I am looking at a possible rental in Cancun. The ad doesn't mention an AI fee, but I know when you "exchange" timeshares, you have to pay it. How does this work as a renter?

Thanks,

Elizabeth: Some resorts have a mandatory all-inclusive, and for others the all-inclusive is optional. You can use the ask-a-question link on the posting page to contact the owner or agent and find out how the all-inclusive works for the week they are posting.

Thank you, I did but never got a response. Thanks!!