Prostitution should be legalised... but:

* It should pay income and sales tax. In exchange for this, legal prostitution would enjoy the full protection of business law. It would also be possible to arrest and convict those who perpetrate violent acts on prostitutes;

* Prostitutes should enjoy the full protection of labor law, including the right of unionize. The state shall have the right to set a minimum age to be a prostitute;

* A legal prostitute should do at least one year of full time study in a community college, with course work on the physiological, psychological, and sociological aspects of human sexuality;

* Legal prostitutes should undergo frequent medical examinations;

* The siting of brothels would be subject to full power of local government zoning authority. Hence prostitution would remain illegal in most locations;

* Legality could be confined to brothels. I have no difficulty with legalizing brothels while keeping streetwalking an offense. I would even hold still if solo call girls remained illegal. The advantage of legal brothels is that they would have procedures and policies, and would keep records. The freelance call girl is impossible to monitor and regulate. 

* The law should encourage brothels to be organized as business partnerships, with each prostitute being a partner. The law should discourage all forms of explicit and implicit pimping.

Look at how hard it is to open a bar or liquor store in most USA neighborhoods. It would be even harder to open a brothel, even if they were fully legal.