In Australia, the exact law varies from state to state, but its legal in all states in some way. In my state it is legal for anyone over 18 to sell sex to anyone else over 18. Brothels are also legal but must be approved (theres one in most large towns), and theres all the usual protections for health and against pimps etc.

Im fully for it as I beleive it is not immoral etc., and that legalising it makes it safer for all parties, and can also reduce the crime around it.