You'll need...
a) an app or game you've made
b) Paypal or some other money transfer method
c) how much money you want from each sale
...and that's it. At the end of the month, I look at the books and see how much is owed to you, I pay you; everyone's happy. If you're wondering how I can possibly earn any money this way, I charge the customer the commission, not the developer. It's done in pound sterling; I add an extra £1 to however much you want from each app, and each time you upload a new app that sells, the fees go down by 10 pence; so all your apps drop in price each time you upload a new one which sells a copy. That pound pays for things like hosting costs (which I'm already in debt for
), advertising, my time and hopefully enough cash to do cool stuff with.
That might seem Bill-Gates-software-baronish, but developers could buy heroin with the money they make and I probably wouldn't care. I'd likey be concerned, but they're your veins and it's your money.
Oh, and return for that, you get a free shirt. And a heroin addiction.