I am in a position where I am hoping to buy this Gears of war 2 forum...
PR is 4... and it gets 15k uniques monthly & still is growing..
my question is.. is it worth buying it for 2.500?
i would know i can get money from ads, and hopefully integrate a system where i can have memberships, tshirts, give away contests, and such.. what do you guys think?

There are a few varibles you want to know. Where is it getting it's traffic from? How much money is it pulling in per month? Check the backlinks then site has are they temporary or permanent backlinks? What improvments can you make? Has the niche got monetary potential?
just a couple of questions of the top of my head

Indeed, Personally i would make sure plenty of its traffic is organic from google/msn/yahoo/ask

See if its monetized currently, and figure out how much its already making, The going rate for a website is around 10 times what it makes monthly, If already monetized. If the forum made $100 a month, Expect to pay 1,000. So with you paying 2,500, I'd hope its making 250 a month.

And as chris said, Check the back-links with yahoo site explorer. Make sure it doesn't have plenty of links from link pages, or perhaps the sellers other sites, You're looking for links that will just get taken down as soon as you buy.

I would honestly look at 15k hits a month, and figure id get 8-10k once i take ownership. Always prepare for the worse.

Also think about the subject, Gears of war 2. That's not like owning a counter strike forum, or a WoW forum.
Gears of war isn't going to gain ANY more popularity than it already has. So as for the web sites future? You can grab more of the GOW2 traffic, but as time goes on, that traffic source is only going to dwindle more and more.

All the above is just my opinion

There must be a reason hes selling it.
Gears of War 3 perhaps? A little close to the present.
Maybe statistics are showing a decrease in Gears Of War 2 players?

Imo: Theres a lot more beneficial things you can invest $2,5000 in!

GoW 2 Only?

If it was a gamer place, maybe you could argue that it will always be updated, but games like GoW aren't around for ever, and your proof is right there, Gears 3 is almost out, so why bother?

It's like buying a VCR player!

Lol nicely put Naz

But they are right. The activity as it is now may increase for now, but probably not much longer after GoW3 is released. At that time you probably won't be able to sell it to somebody else for the price you bought it either, so you'll really have to make money only to break even.

Depending ont he domain, you could ofcourse expand to GoW3 (and GoW1) material. Either way, you gotta act (or not act) quick

It is a lot for a forum, but it may be worth it if you can monetize it well enough? Just me personally, ad wise I'd probably go for selling banner space (beyond just adsense or something) or seeing if there are some CPA offers you can run that pay out well and you think would convert. The forum has a large user base, is there an affiliate product you could promote or perhaps a guide/ebook/video tutorials or something of that kind related to GoW or whatever the majority of the members are into and see if they would be interested in purchasing? $2.5k is a lot, I wouldn't pay it myself BUT if you are fairly certain (and have done your homework) that you could make much more back, then why not?