The online bingo market matches your spec
"I am interested in something, where there are no download-able software, all the games are played online. I am also interested in game rooms, with on-line chat etc."
the baisc business model is that you license the software and pay a fee in return. The fee is usually a cut of net revenue (ie how much your players lose). Depending on the supplier you went with, you would also get hosting, customer support, banking and bandwidth included. You just do the marketing.
If you want to go down the softgaming route, there are a number of places where you can get 'white label' scripts for free. See
http://www.gamecolony.com/affiliates.shtml#2A or
http://www.mygamescript.com/.