I hate to be a wet blanket here, but I'll have to go so far as to say, yes, it's most likely deemed immoral (I'll leave the legal aspects for individual research). I've been pondering this topic at another discussion board- on the mertis of legalized prostitution, and have come to the following conclusions. Keep in mind the following arguement is generalized, but I believe sets up a strong caset.
Prostitution might be viewed as sex between consenting adults, with a nice capitalistic spin, witht he prostitute enjoying their work. No problems with that, right? Probably not, but I think that in a vast majority of the cases, that is not the situation, which leads to a strong argument against prostitution and this minor endorsement of it.
It's a very unhealthy and dangerous job. Though it gives a quick cash flow it also has several draw backs, including the legal problems, violent and dangerous employers, diseases, accidental pregnancy, and once a prostute's looks are gone, they are left with little or no job options. Coupled with this is usally substance abuse, which compounds the problems this trade offers. The job attracts runaways, addicts, and people using this as a last resort, and because of that, the johns/pimps are exploitattve in nature.
In this case, you'd be paying for tickling. While though not as bad as paying for sex, it is still an encouragement and contribution to the exploitative nature of prostitution. You maintain and support the lifestyle preclusive to this. In the classic moral sense- there are two sins- sins of action and omission. By supporting prostitution instead of working to make a better life so people do not have to fall back on such a choice, I believe it sins on both acting immorally and failing to stop the spread of what may be immorality.