I don't know what the laws are elsewhere but in the United States, prostitution is illegal (except for Rhode Island and parts of Nevada).
In my opinion, it should be legalized (everywhere) because it's doing more damage then good if it's illegal. This is the type of business that, whether it's legal or not, would still happen. By legalizing and keeping tabs, it'll be much safer for both client and seller. As for children getting involved, well this is the reason why we need to keep tabs. We could be using all that energy to track down rapists and such then to arrest consenting adults for doing the deed for money. It's simply a waste of resources that can be used to do something more productive.