Canada recently changed its laws to keep it illegal while exempting the sex workers, themselves. In other words, if a prostitute gets beat up by a client, they can report it to the police without fear of being prosecuted, themselves.
It's legal to sell sex, but illegal to buy it.
It's legal to advertise oneself as a prostitute, but illegal for a third party to publish such an ad.
It's legal to solicit a customer about prostituting oneself, but illegal for that customer to solicit the prostitute.
It's legal to profit off sex if you are the prostitute or someone to whom the prostitute is "legally or morally obligated to" (read: family), but illegal to profit from someone else's prostitution (read: pimp).
^^ This all sounds OK to me.
In the U.S., as far as I know, it's strictly illegal (buying OR selling). That seems a bit much. The prostitutes should have some kind of protection (which is why Canada changed its laws).