Posted 16 May 2013 - 11:03 PM
As you point out, your app will not be allowed in the major app stores, and also some ios devices won't allow you to install non-market apps.
Both are barriers that you will need to overcome.
Not that your app is porn, but as a proof of concept there are many porn apps out there you can find on your favorite search engine. There is a market and there are many people willing to go through the extra hoops to get the software.
If you choose to keep your software adult themed, you will need to get them motivated to cross the barriers.
It will be your job to identify your customers, market to them on whatever sites they visit to get them to your site, and convince them to download and install the untrusted app directly. You need to convince them to go through those extra hoops. That is where you need to spend your marketing money.
The difficulty will be one of marketing trust and brand awareness. That gets expensive but can absolutely be accomplished.
Exactly how much it will cost in marketing before you start getting enough revenue to offset it is a much harder question.
Once your customers have brand awareness (they know you exist) and they have trust that your apps are not viruses, and you remove as many barriers as possible such as allowing the link to be texted to a phone or emailed to be picked up on the device, your customers will follow.