Payment processors for adult sites: what they actually ask for

Almost everyone who starts a directory discovers the same thing in the same order: building the site is the part that goes to plan, and taking money is the part that does not. The big processors decline the business outright, and the ones that accept it ask questions that have nothing to do with software. Knowing those questions in advance turns a three month stall into a two week form.
What they actually ask
The first question is who you are, not what you sell. A registered company, a business bank account in the same name, the identity documents of whoever owns more than a quarter of it. A processor that accepts adult content is taking on the risk of your entire operation, and it will not do that for a name on a website.
The second question is what happens when something goes wrong. Who checks the ads before they appear, what makes an advertiser get removed, where the complaint form is, how fast you answer it. They are not being difficult: card networks fine the processor when a merchant attracts complaints, so the processor wants to see that you catch problems before their systems do.
The third is the one people forget: how you know your advertisers are adults and are who they say they are. Identity verification has stopped being a feature and started being a precondition. If you cannot show a process, expect the conversation to end there.
What to do before you apply
Register the company first, in a country whose rules you can live with, and open the bank account before you talk to anyone. Write your rules for advertisers down as a page on the site, not as an intention. Turn identity checks on from day one, even with three advertisers, so that the process exists and can be shown. Then apply to three processors at once, because at least one will say no for reasons nobody explains.
The mistake that costs the most time is applying early, being declined, and applying again to the same company six weeks later with the same file. A declined application is remembered. Prepare once, apply once.