What kind of site are you planning? a paysite or a site to promote paysites?
Don't get me wrong - but to make a SUCCESSFUL fetish site you need to know the fetish very well - the more special/weird the fetish is, the more important it is to understand it. That's probably why only a few % of all adult webmasters do fetish sites
If you want to promote some cool niches and need some input on what to promote feel free to hit me up
