Hey, LocalMonero staff here.
The fee is explained on our fee page: https://localmonero.co/fee
Essentially, the user who is the one that posts the advertisement is the one that pays the 1% fee. If the seller is the one who posts the ad - then the seller is the one who has to pay the 1%. If the ad is posted by someone who wants to buy Monero - then the buyer pays the 1% fee.
You can contact us by telegram @LocalMonero if you have more questions. We're also easily reachable on reddit (/r/LocalMonero) and twitter (@LocalMoneroCo).