The prostitution aspect itself is not a problem, according to my moral code.
The problems I see are:
* The economic system where people need money to get basic needs met, which drives some people to desperation and all sorts of crime, including prostitution, which they would otherwise not do. I think it’s terrible if someone would not want to prostitute themselves, but end up feeling it is their only option.
* Drug-addicted people who start needing lots of money, and so sell themselves for money for drugs in a self-destructive addictive spiral.
* Bad pimps of all kinds.
* Any situation in addition to the first three that causes forced / coerced / obligatory prostitution, and/or takes advantage of the situation.
* Dangerous situations that can come up unless well managed. STD’s, power issues, etc.
* Mental health and maturity issues.
* The illegality adds problems to the situation, since it leads to secrecy and the unavailability of help.