Legitimate sites will either be free or require you to purchase a package.
Although sex has its obvious physical attributes, sex is also a form of communication; the canary in the relationship coal mine.
And a relationship where you refuse to communicate about this lack of communication can’t be fulfilling.
It’s also a good idea to create a unique email that you only associate with that particular site.
Sometimes, dating sites like to inundate you with spam.
One of the first sites I ever had success with was Adult Friend Finder.