The org extension isn't a good idea if you're going to use pinkforum for an adult forum (remember Hustler magazine's slogan: "think pink").
It sounds as though you have already made up your mind to buy it. If that's the case, make a reasonable offer...It's hard to give advice if we don't know your budget or the asking price.
It's not a popular domain, so why not ask the seller what the asking price is?
if your budget is $200 and there's no asking price, offer $75. If your budget is $500 and the asking price is $300, offer $150. If the asking price is $x,xxx, politely explain your max budget was $xxx, and wish him good luck. If he's at all interested, he'll respond to you.