The Shotgun Approach
Unless you have time and a good financial backing, it is not likely that you can make a major effort at marketing research. There is a way around that, though, in which I feel very confident.
Not everyone believes in this approach, though. Some very successful webmasters have only one or two sites and focus all of their energies on that site or sites. But many more webmasters who followed this approach are not successful and eventually quit.
What I recommend is to put up a large number of small sites of various types. The age verification systems are perfect to work with this method.
If you are using an avs, you do not need thousands, or even hundreds, of pictures. You can put together a small site with 20-40 pictures, using a lot less time and money. Put this on an avs and see how it goes. Check your conversion rates. Put an e-mail address in the inside and request comments.
Meanwhile, do the same with other avs's and other content. See what works. If you have a certain site which is well received, then you can spend your time and energy to expand that success. Make a membership section within the avs, or maybe expand the site, get rid of the avs, and make it a pure pay site.
If a site doesn't do well, then just leave it alone. If it generates a couple hundred dollars over the course of a year, well then that's a couple of hundred you wouldn't have had. But don't waste your time and effort when the same time and effort can return higher returns elsewhere.
This may sound familiar to those of you who have been in the military. But the concept works just as well here.
Don't forget to link each site to each other. This is why you use different avs's. These surfers have proven that they are willing to pay for age verification. Convert them to other avs's where you get the sign-up.