Flat Fee advertising

Hi

I have an active forum of 4K+ members. Now i want to earn money. I have ad-sense account however i want to know from where do i get Flat Fee advertiser for my site ? this way i will be assured that i will be getting certain X$ per month.

You can search on other forums, related to your niche and ask their admins to advertise on your site. You can also ask your members to advertise on your site by paying a decent amounts of money. Provide different offers and promotions for advertisers. Make user-friendly environment for advertisers. In this way, you can attract more advertisers towards your site.