1. General classified ads, which can be used by anyone and place ads on the sale of any product, rental property, job search. In General about everything. But in order for this project to work you need a very expensive mass advertising. Message boards even advertise on TV. How to promote such a portal without expensive advertising I do not know. 2. Choose a narrow niche. For example, a classified ads for the sale of land in a particular region. Discussion of a similar idea is in the topic: Internet portal started from scratch. In addition to land it can still be building materials, jobs, cars. Then you can without large investments to promote the project at the regional level. And it will have interested visitors who will buy the services of the Board. For example, VIP status or place your ads for money. 3. Choose a wide niche, but focus not on people, but on search engines. On such a Board, you can copy ads from other sites. Then the Board can get big, but it will not be interesting to people, because when copying will come across irrelevant ads, and search engines will send people to competitors. Search engines are not willing to index such sites as far as I know. To search engines indexed pages, apparently have to invest money to buy links to these pages. And most likely you will have to earn by selling links. Links on message boards are cheaper than on other sites. Therefore, it is more profitable in this case to create not a Board, but a copy of some other sites with simple articles. Then links can be sold more expensive. 4. To create such a Board, on which the people themselves would like to place ads. The difficulty is that on the Internet there are promoted boards in all known directions. And to lure people from there is quite difficult.