The trouble with trying to cross-fund ventures like that is it might diffuse the focus of your business. The way you succeed is by doing what you do best, which is ideally better than the competition and something that's in demand.

I'd say you're faced with a few ways of raising capital, one of which is investing in a porn site. While web sites may be web sites, I'd suggest that running an adult-themed one is more problematic than most because people will always think themselves clever and try and crack their way in past your pay-wall. Without the right precautions, this could take a fair bit of time to either set up or, in the case of breeches, to patch up the compromised accounts.

If you don't want to get directly involved, you might want to consider exploring what you can do to make money from that sort of thing without running a site yourself. For example, this friend of yours may need some technology developed for their properties, and as you have many developers on hand, it could be trivial to crank out something like that for profit without impacting your other project too badly.

That way you get better at doing what you're best at, such as development, without getting distracted over the long-term with other side projects.