In terms of sex, there is no difference. Both are illegal in most states. (Some localities in Nevada and a few other states allow prostitution.) That said, if an escort agency is merely offering female companionship - say taking someone to a social event - then the difference between it and self-employment is merely one of convenience. An agency basically acts as a clearing house - a list of women who presumably meet whatever standard the agency says it maintains. By contrast, a self-employed woman - and frankly I have never heard of a self-employed escort who was not a prostitute - is the totality of the man's choice. He may look at the woman, maybe even talk to others who have used the woman's services, but there is only two options, pay her and utilize her services or don't. From the woman's side, an escort service nominally provides the girl with access to a wider list of clients and at least nominally with a degree of safety. The agency may provide security or make a brief evaluation of the client to see if their "agent" - the woman - will be safe. The self-employed woman is on her own and can only depend on her own contacts. Of course, ALL of this is highly theoretical. Many - if not most - escort agencies merely front for prostitution rings. The woman is really no safer and some - if not most - of the money she makes ends up not in her hands, but the agency's books. I used to work for something called the Helsinki Commission, and one of the issues it monitors is the international trafficking in prostitution. You can count on one finger the number of services that are legit. So, basically, what you are left with is that the self-employed woman and the woman who works through an escort agency basically end up in the same place - and that usually is NOT a good one.