In many states, country's or regions, the official job working as a escort might or might not be allowed. It depends on the law and in most country's prostitution is allowed but only under the condition that the female is a independent. This means that no agency nor man in the middle could negotiate a price in between the girl and the client, while getting better financially of it. The law in this case requires the girl to work independent and plan her own bookings.
However in various country's the work as a escort girl is legal and simply falls within the independent line of duty. A registration is required as a sole proprietorship, administration needs to be filed in on either quarterly or yearly basis, and tax needs to be paid. In some country's girls who work in the business actually save for their own pension due to the legal acceptance as profession, but in others you have to take of this your own.
Another problem is legal working as a prostitute. In some country's it's forbidden, and getting caught, end up in problems or encounter a violent situation, it's nearly impossible to ask for legal help as such legal justice by going to police. If you ensist on working in the adult business, it's best to aim for a country where it's legal. On the page of countrys you can find more detailled info based on the local law & rights of sexworkers. This is still in progress.