Unless you have decent traffic to send, I personally wouldn't recommend adult - it's a tough business and payouts have never been worse.
In regards to content - no need to buy it...many adult sponsors provide lots of free content to start with ... a sponsor I've had good success with is NastyDollars.com.
2257 applies to those who shoot content - stick with "stock" photos and you should have no probs - no guarantees of course, but unless you're promoting underage stuff or really explicit content (rape, scat, blood, etc) you're likely not going to be targeted by anyone.
As I said above, 2257 is for producers and generally not something you need to post on your site - if it makes you feel better, you could put a link to the producer's website 2257 notice and/or to a redacted copy of the models contract (some companies will provide them upon request). Personally, I wouldn't worry about all that stuff for the reasons I wrote above.
If you have general traffic - you'd likely do better to send it to non-adult affiliate programs...click over to Commission Junction ( cj.com ) or LinkShare - or perhaps even try Google's adwords if you already have some developed websites.
Hope that helps...
Oh lastly, since this is the adult sales forum...here are some select adult oriented domains for sale:
(domains listed for sale here deleted)
Ron