It’s certainly legit but, as with other sites, mainstream and casual alike, you will get members trying to scam others. AFF tried to weed out the likes of escorts offering services for money but people can be slippery and devious. So, as with other sites, use common sense. In order to be able to message other members, you need to pay for a subscription so that very fact deters a lot of scammers.
In terms of getting a hookup then the membership gender imbalance means guys have to work harder and stand out, especially if they are not particularly good looking or lack an athletic build. Women do go for charm and charisma as well as looks, so the sheer numbers on the site mean the potential is there for subscribers to get what they are looking for.
The best advice is to either try it for free with the limited services or try it for a month and follow the tips in our article on Adultfriendfinder profiles, messaging, and profile pictures.