The escort business it self isnt illegal, its just that the girls tend to sell sex. Thats the part that is illegal. So as long as you moderated it and kept from obviously stupid posts like "suck your dick for 20 dollars" you will be fine. Have the girls that sign up sign a disclaimer that they wont use the site to sell sex because selling sex is illegal. And have the johns sign a disclaimer thats somewhat similar. If you use your search engine im sure you can find such a site , and im sure they have said disclaimer you can spin.