yeah, it's illegal....especially if you paid for it. If you paid, then you'll get hit with prostitution or soliciting charges; and if you claim it was consensual, then you've just admitted to public lewdness.
the amount of trouble will depend on where you are, and the local temperature with regards to "massage parlors." it seems that every summer there is an increased focus on the international sex trade and immigration.
it's not worth the $60 for a hj. get a girl friend and you won't go to jail.