well, the easier and most convenient way is to ask
FDSign to build you a site with all the features you need
.
But depending on your skills, you can also buy this
membership script (besides being the best, it's the only one made for adult WP) and then play around with options and test what works for you.
But in the end, you gotta know that WP is just a CMS (the best known to date, of course) and no matter how good is your CMS and/or your membership plugin, if you don't know how to build a site, then you'll have problems anyway