Agreed. Excellent advice. Don't expect to make a profit on a forum immediately. They're great long term investments, but very very rarely ever turn any type of real profit in the short term.
I found that niche forums do the best. ONe of the largest forums in the world is a bicycle forum. Niche music forums do well. Dance music, hip hop etc. Find a niche market that not many people have touched on. Deep sea sport fishing such like that so that your forum reaches a certain audience then cater to them. Your adsense revenue will come easier if you are not competing with millions for business. Your members will come easy because there are only so many sites in the field of your choice. I new a guy who had a hardcore orginal music site. He had over 2.5 million bands who were unsigned and they put their music up on his site for others to listen too. The revenue was insane.