I suggest you get
Strongbox and
Throttlebox. The pages describe what they do. In short they stop scum getting into your site and raping all the content.
How much content do you have to start off? Asking models if they want there pictures and videos spread across the Internet suggests you may have a model release. If you do then fine, if not then get them to sign one. You can hit me up on ICQ and I will send you the ones we use. What IDs of the models do you have to prove the girls are over 18?
Using the sites you mentioned as examples is great for the style of the content, I believe these sites have been going a long time. Starting up now and shooting that level will take money unless you have a lot of content to kick it off. Or a lot of money.
I'm assuming you and your photographers have the skills. Do you have access to this level of models and the locations? These sites have some stunning girls, many from Eastern Europe. MC Nudes I suspect has Czech girls because I'm blocked from viewing it.
The hosting side is easy to get right and cheap. The content side is a nightmare and expensive.