Spend the ten grand to shoot content. Get 10 girls/10 scenes, or try to do better. Shoot where it's cheap, get newbie talent, pay as little as possible, collect content, gather it, get a stockpile.
After you've spent every dime spend another few hundred to get a paysite designed. Hosting, billing, etc.
NOW: GO!!!!!!!!
Oh, you've spent all your money already? Where ya gonna get the additional $5-$10K+ needed for advertising, traffic, etc etc?
SEEYA! Buy GM stock instead.
Of course, the last bits can be factored in, and you can go VERY far with sweat equity. So it really all depends on how hard someone is willing to work.
BOTTOM LINE: If you could just throw ten grand at something and make money with little to no effort, even if the ROI was a 'measley' $1000, or 10%, we'd all be doing it.